Yeah, I've looked and not been able to find one of that size. Not a big deal really, but would be a nice touch to finish it off.If you want to use an O-ring, you'll have to find one the has a groove cut in the oitside edge (and the has a diameter of just over 2 in, so it will stay in). You may have to cut the groove into yourself (watch the digits). It would work just fine, but I decided on getting the complete kit.