Where can I get a brass float made for a Kingston L carb - have problems with the cork ones and the gas we get now. For Holt 10 Ton. Thanks

Not sure about replacing that float but what you might try is to thoroughly dry the cork float and dipping it in gas tank slushing compound and letting it dry. A good epoxy, such as what you'd use for fiberglassing would probably work as well. Besides gas proofing the float, it'd keep it together instead of letting it fall apart as I've seen the so many of the old cork floats do.
Depending on how much weight was added to the float during this treatment you might have to change the float height a tad to compensate.