Best T/T Pods/ wood blocks to eliminate vibrations

My table is 3 feet from the right speaker. When the tonearm is in play, knocking on the table plinth or dust cover creates an amplified thumping sound. The table is a Rega P3-24 and has THREE rubber cone feet that are not removable (There are two in the front and one support in the middle at the back of the T/T. The table sounds good, but I know that feedback is degrading the sound. Need recommendations for either footers, pods, points, or blocks to eliminate that thumping sound. BTW, I can not use a wall shelf because the walls are concrete, and also cannot be drilled
Regardless of what miracles are promised by footers, if you thump the turntable when the arm is in play you are almost certain to get a thump in the speakers.

There are turntables and isolation systems that can eliminate this at the floor and even at the stand but if you move to the dust cover and plinth itself what you describe is normal.

The Vibraplane system can eliminate all floor borne vibration and eliminate all feedback but unless purchased used the cost is more than the Rega.
The best bang for he buck by far that I've found is Herbie's Tenderfoot Isolation Feet. I replaced the Sorbothane suspension with Tenderfoot footers in my VPI HW19 Mk4 and the improvement was not subtle. I would think that they would work exceptionally work well under a suspension-less table like the Rega.
I use a Gingko platform designed for regas (I have a P9). Works wonders for isolation.
I don't think any of these devices will eliminate vibration. Some may be more effective than others. I experimented with spikes, pads, wood blocks and have found they pale in comparison to a proper vibration isolation platform like the Vibraplane system. There is simply no comparison, but as Albert points out, it is much more expensive.
But Albert's first statement is also correct, IMO. No matter what you do, it is unlikely to protect against a direct rap on certain parts of the plinth and dust cover. The best cure for your stated issue is not to rap on the plinth. Which brings me to a question: do you have the dust cover down over the platter whilst playing LPs? I think that's a bad idea. In fact, I suggest you remove the dust cover entirely from the plinth while listening to music. The dust cover can easily serve as a sounding board which will effectively amplify acoustic feedback to the tonearm/cartridge, both efferent (the faint musical signal that can be heard with your ear near to the cartridge) and afferent (ambient room noise and the sound from the speakers). As to the rest, there are a myriad of strategies to better isolate your turntable; all of them have their pluses and minuses. Even the Vibraplane can be a problem if your turntable has a spring-y suspension of its own.
I have this Table, And It would do a world of good if you had a rack with a shelf on points, then make sure your table is LEVEL check this by putting a horizontal level on the plinth then on the platter too. SO,the iso feet you choose should be all the same exact height and not to soft.Some small pucks or disks.look for something like that. And I cant stress enough to have the table on a rack with points on the floor and a shelf with points also. Heck with my rack and shelf I don't even use iso under the table.But if I did ,I would use something like i described.
i had the same problem n went to walmart n bought a 12.5" bike inner tube put alittle air n sat the turntable on it adjusted the air so the feet r 1/4" off the stand..(air ride)works 4 bucks u will ever spend
I know this is kind of an old post but just wanted to let you know I have had an issue with rumble from my subwoofer and Planar 3 table when I turn the volume up loud. It was mainly due to the placement of table. I was getting this terrible feedback loop. I ended up using Sorbathane 2.5 inch half spheres under the feet. I placed them flat side down on the shelf and round side under the feet. This completely eliminated the feedback issue. I can beat on the shelf right next to the table with my fist and hear nothing from the table.