you can get a nice carb for less than 150, search ebay under ALL categories, and type in (oko carb) and have a look, i have a 30mm oko, its a very nice carb easy to tune, but if thats too small, thatn a used 34pj might be another option like mentioned
there should be atleast one in the states, but if your not in a rush you can get one from ebay seller from taiwan, it will take a bit longer, but the option is there. its a keihin replica, and i use keihin jets in mine.