Upgraded power cord to fit my Vandersteen5A's

Try one of these http://shunyata.com/Content/products-UniversalAdapter.html

Then you can use any power cord!.

I had the same problem with my Von Schweikert db 99 speakers. I found that the Shunyata Diamondback power cords fit, make a big improvement and can be found on the used market for a fair price.
Regards,

I tried Audioquest power cords on the Quatro with zero benefit in sound, I personally dont think its worth it, besides its below 100hz, what do you expect to hear anyway?
Its not going to make bass tighter or anything else IMO.
PS,
I am a firm believer in upgraded power cords, use them and have heard a gain in sound on many occasions but in this situation at these frequencies I dont see it happening, IMHO. Cheers

The Audioquest NRG-10, 4, or 2 will fit you can see them online at Needle Doctor.