there are couple ways to go.
the first would be to try and repair the diaphragm. people have used vinyl repair kits... the kind you use to repair those cheap vinyl swimming pools.
second would be to buy a used set of carbs and switch out the diaphragms. a full set of carbs usually run about $100 on ebay.
last would be to purchase the parts new from an online source.
personally, I'd try to repair it first. what have you got to lose?
