Two ideas. First is Carbking out of Missouri. The Carburetor Shop: https://www.thecarburetorshop.com/

Second would be Marx Parts is a frequent contributor that sells and rebuilds fuel pumps among other items. I don't know if they have a source for float bowls or could repair yours but they might know someone if they don't. At worst it costs you a phone call and a few minutes.

https://marxparts.com/?no_redirect=true

@tiny @arthur-c-winters I would not recommend JB Weld for this repair. I know they claim to be a suitable repair for gas tanks but I found this to not be the case. Gary Wallace in St Louis Missouri has a good offering of 4 Cylinder Chevy stuff. He might be able to help. chev4cyl@charter.net

Mike

Another thought on the float is to use Gas Tank Sealer solution.  (look up Bill Hirsch gas tank sealer).  Don't dunk the float in it.  Use a small artist's brush and brush several light coats over the leaking area.  Gas Tank Sealer is designed for the fuel system.  And of course, be sure the float is cleaned and prepped properly for good adherence with the sealer and get all the fluid out of the float first.

The float was repaired by a member of the VCCA club here in St.Louis.  He was also able to get all the gas out of it, before he soldered it.  This problem is very real as floats are rare.

The Zenith carburetor floats present a challenge. If the only crack is on the outside then it can be soldered after the liquid inside has been removed. However if the crack is in the center passage (where the needle must move freely) then soldering is very difficult. Used replacement floats are not plentiful but a little more available than hen's teeth.  There was a fabricator in England that announced several years ago that they would reproduce the floats. Unfortunately I am not aware that they actually did it.