125m replace petcock seal on carb?

[rdlsz24]

So I picked up an '84 125m last Saturday for 75 bones. It runs fine but needs a little tranny work. Anyways, when I put it in the back of my truck I turned the petcock on the carb to off and the o-ring around the lever disentegrated and the gas started pouring from it! I see Honda only sells a gasket kit for the whole carb, but since it runs good I don't see the need in spending $20+ and tearing into a good working carb. Can I just find a little o-ring to replace mine? Anyone know the correct size or where to get one?

Rob