Customized Silicone O-rings

[fijistic]

Do you guys know where I can buy customized silicone o-rings from?
By customized, I mean measurement of depth,size...etc.
I'm trying to customize my keyboard with those silicone o-rings.
And no ! don't tell me to buy those rubber o-rings. It has to be the silicone ones that looks like this:

http://www.ebay.com/itm/V060-Replacemen ... 1c20a08e21

[thegunner100]

http://www.mcmaster.com/#o-rings/=ids68s

[dorkvader]

Don't they only have 70A and 40A?