I have loads of quilted melania snails, closely related to malaysian trumpet snails but don't seem to reproduce quite as fast. I stripped down a 75 earlier tonight, (moving the tank to make room for the 125) and found the sand pretty well covered with good-size snails after the tank sat for a while with just enough water to cover the bottom. I never suspected there were so many in the shallow sand bed.
Also have ramshorn snails in a couple tanks, brown and red mixed. Shipping out a few hundred (mostly browns) for feeders Monday, but there are plenty more remaining.
Either/both are $1/dozen + shipping.