These aren't exactly cheap, but OEM Carter.
Carter 21-252 Carburetor Float - Carter Performance 4-BBL ThermoQuad 800 CFM | eBay
I've bought from these folks several times. They're good people. I had a problem once and they took care of it immediately.
If you check the "Save to Watch List" button, in a day or two they will offer you a slightly discounted price.
I don't know if these are the exact floats for your TQ, so be sure to check.