Where to find LP clamps?

Twenty years ago I remember there were clamps you could put over the spindle to secure/level a LP. I'm considering putting my turntable back into my system and I'm wondering where I can find these clamps if they're still available.

Anyone know where I might find these clamps and/or know if they really make a difference?

Jerry Raskin's Needle Doctor has a pretty good selection of record clamps at various prices. Take a look there and see if you can find something that will work for you. Sean
Of course they can make a big difference. Certain clamps work with certain spindles (threaded, unthreaded) & different clamps sound different on various rigs. You have to experiment (or perhaps query the experiences of others). Many analog vendors such as Acoustic Sounds, Music Direct, VPI, offer record clamps for various applications. The most expensive clamp won't necessarily work best; you must try them out yourself. The very heavy weighted clamps have been known to cause spindle/bearing wear on some turntables.
A good-quality, inexpensive clamp which can be used with just about any standard, non-threaded spindle is made by England's J.A. Michell. The black-colored version is a lightweight design made of non-resonant Delrin with a knurled-aluminum-knobbed collet mechanism for secure fit, and you should be able to get it from Michell dealers for around $45-$50. It made a definite sonic improvement on my 'table, most notably in image focus and transient articulation, and of course they help with less-than-perfectly-flat records. However, before clamping your records, make sure you're using a mostly flat-surfaced mat which effectively damps the platter and doesn't reflect energy back to the stylus/groove interface.
I used to use the VPI Derlin clamp with the TNT I used to have. Upon getting back into analog with a MMF-7, I have been told that a "Ring-mat" without the clamp is the way to go. I would have to agree and haven't gone back to the clamp yet. I had intentions of using the clamp prior to buying another table to. Listen and enjoy the music :-)
...so, you want to find first clamp and than match the turntable??::))

Don't go for Sota or VPI clamp that realy can only make the record placement worse than it used to be since they're too heavy.

For a proper clamping you need to very slightly couple the record to the platter or mat (I would recommend a donut-shape mat to use with clamp)

I have Michell Gyro SE turntable with Michell clamp that gives me an extra flexibility either to firmly couple the record to the platter or just place it without locking that couples it slightly or not to use it at all. I all three different situations you should realize that the sound is different.
The first described situation I use on extra bright vinyls with poor mastering. If I lock the clamp my record will be firmly coupled to the platter and there will be a significant roll-off of high freequencies with even vast sacrifice of details. If I use no clamp I get airy presentation that is very suitable for small bands. In second case unlocked Michell clamp adds a tonal control that I often use for sophisticated instrumental and electronic music which is probably 70% of my entire collection.
Marakanetz, I have to take exception IMO to your description of firm clamping as causing a 'vast sacrifice of details'. The HF attenuation you hear is the reduction of spurious resonances in the record itself, which although sometimes regarded as adding pleasant (if inaccurate) 'air' to the presentation, are not increasing transparency to recorded detail - on the contrary, they're reducing it.
I agree with Zaikesman. The same thing takes place when folks use "springy" unsupported platter mats such as the Ringmat, etc... These types of devices artificially boost the high frequencies, making a dull recording or improperly matched phono system sound more "alive" and / or "open". Under extreme test conditions, one can even measure reduced tracking ability when using unsupported platter mat's. As such, all they can do is reduce a phono system's ability to perform to full potential. Sean
I might argue on that since Michell uses an acrylic platter that I cannot consider it "springy" or unsupported and the clamp realy works best if only applied without locking on the Michell. The same I can say about Oracle tables where you should only slightly screw the clamp to touch the label. Simply saying when you couple a record directly to the platter the minimal clamping is sufficient and best.
M., you are correct in pointing out (as I also referred to in my first post) that the platter/mat situation makes a difference in these regards. In addition, I do think it is possible in some instances, with a soft mat and a thin-vinyl pressing, to 'over-clamp', deforming the record and placing it under stress. Although I doubt that the light weight of the Michell clamp by itself, untightened and acting merely with gravity, could have much of a positive effect (in fact, it could have a deleterious effect if allowed to vibrate), at least we agree that it is a good clamp at a low price.
Thanks everyone for your ideas/suggestions/discussion. It's been enlightening!