Where to get protective cups for under spikes?

I agree with Davemitchell, use quarters. First I used a 3/16" drill bit to put a small crater in each of eight quarters (for the spike point to ride in). I then glued the quarters to a piece of leather. After cutting out the quarters/ leather pieces I placed them under the spikes. The leather protects the floor from scratching and the small crater keeps the spike in place for final positioning tweaks.

Acousticsounds.com

The Lovan Footer is a great product; available in black or chrome

Plenty of places on-line for about $1.25 each. Do a search for audio spikes and find a couple of the catalog companies. Same material as the expensive stuff, coated brass.

Sound anchor sells what they call "Conecoasters" for 14 each. I am not sure if this is cost effective or not but seems like an option.

Personally, I am interested in replacing original spikes with soundspikes. However I don't know the size of Sound Anchor spikes and not sure if it is possible. Does anyone know if they are M6, M8 or any other size?