The manual choke carbs are a lot tougher to find than the auto choke carbs. I believe this to be because of those using dual and triple carbs want the manual choke versions.

If you don't mind an automatic choke (I don't personally like them myself); it is relatively easy to install an automatic choke carb replacing a manual choke. The only issue is the heat for the choke. That may be provided as follows:

1) acquire a piece of roughly 18 gauge sheet metal 6 inches by 3 inches

2) cut a 1/2 inch square from each corner

3) bend the 4 sides, making a rectangular "cup" of depth 1/2 inch

4) drill a hole in the center of the cup and install a brass fitting

5) install the cup on the exhaust manifold with the open end toward the manifold

6) bend a piece of tubing to attach to the brass fitting and the carburetor choke

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop