Just an update: The size, if anyone needs it, is an M12 1.25pitch x 30. I picked one up at the hardware store for about $2 with a washer and it works fine.
you might try giving old bike barn a call.They sell the kit that upgrades the old sealed beam unit headlamps to the modern halogens. they might have the bolts
Shut off valve gasket or the float bowl gasket (O-ring) is what it sounds like Take it apart and clean it first but don't try and remove it from your tank.
I've gone to 3 different ones so far. No one apparently carries metric that size. :/ I'll try Ace Hardware tomorrow, and if not there, head up to a Home