I looked at our farm supply store (much the same as a hardware store, but with more stuff), but could not find any O-rings marked #61. I did find some marked "Industry standard #008" that fit (I took my Victory's screw into the store with me). There was one that was slightly bigger than the 008 that fit too, but I liked the snugger fit of the 008.

I paid 23 cents a piece, and got two.