Hmm. Most hydraulic shops sell the Viton O-rings, And almost all hardware stores sells the plain rubber ones, including Lowes, and the other super stores.
Just the size is the same but the viton O ring is more heat resistant as compared to a regular o ring.
I highly doubt you can buy a viton at the hardware store for 30 cents or so.
It will take a good effort to get the Viton O ring. It does not come in a sealed cardboard pack of 5 that I know of.