If the carb is clean and all the airways are clear I dont see the point of trying to source a new (old) carb, it may be worse than the one you have already?
I would do the cheap things first like borrow a compression tester. Your bike is easy to check as theres room to fit it without taking stuff off first. Cant you ask at a local car garage if they will do it for you for a nominal cost...I mean a repair shop of course not a dealer franchise.
To me we have finally eliminated the carb as long as
1:your needle is in the right notch with the clip
2: The float height is correct at 21mm?
3: The choke is not passing fuel because of an imprinted rubber seat
Do the test of compression next.
Like I said before these things can be much more difficult to find than 'bike wont start issues' in my experience.