Are you saying the float broke, or the cast aluminum bowl cover? I have never seen a broken cover before, only the iron bodies. You might have the cork float, if so save it for a museum and buy the plastic version from caterpillar. You could try a John Deere parts source as well.
They do come up on ebay, there was one a week or so back that wasn't in very good shape, but probably fixable. I have a JD pony carb core, but I'm not sure if the bowl cover will work on the Cat carb...there's not that many common parts when you compare them, although they are both Zenith carbs.
Also try S&S Tractor in Marcellus if you want to go look one over - not too far from you.
Try VE Petersen in Moline Ohio 419-265-8047
Gary