he had suggested an online place to me a while back that carries just about any size o-ring you could want. i can't remember now what the website was but i think there is a 10 piece minimum or something like that......
Let me know the size you need. I am guessing but there is a min. quantity to go this route but they are about $11.00 for a 3-1/4 OD x 1/8" thick Package of 50pcs. They are sold in packages. But $11.00 is still not much for the package of 50. If this is the size you need.
If you let me know what size today I can ship them to you tomorrow.