I followed Steve Maas's suggestion and sourced #204 o-rings, in both red and black, in 100-unit quantities. My source was amazon / o-rings inc.
make sure to get 70A (soft rubber) durometer. I made the mistake of getting some 70D which are hard, like solid nylon, and cannot flex, in white. I am currently sampling some pinball rubber o-rings in white. It's darned hard to find white o-rings off-the-shelf in the #204 size. Nearly all pinball rubber has a 1/4" diameter for the ring which is too large. I got quotes from about 5 outfits to make #204 in 70A white silicone, but the prices were $220 - $400 for a production run of about 250-300.
#204 = 3/8 x 5/8 x 1/8
They fit a tiny bit smaller than campagnolo rings. I am testing samples of :
5/16 x 11/16 x 3/16
in white pinball rubber for the white o-rings. They should arrive any day now. Another person who corresponded with me ended up buying his own #204 black on ebay :
http://cgi.ebay.co.uk/
- Don Gillies
San Diego, CA, USA