The word from the Finnish 1300 riders is that the replacement ones tend to be stiffer than originals. This can cause problems when riding since the carbs do not react as soon as they should. I have always kept the original ones when repairing carbs.
Raygun wrote: If its just a small hole, I would just try to repair it on the top with silicon or something.
Locitie used to make a product called Black Max. It was a glue compound similar to Superglue or Carzy Glue but when it set up it was still elastic. At the nuclear plant we used to make our orings from bulk oring material, cut the ends square and glue them toether with the Black Max. 5 minutes later, you could install. I would think the Black Max would be the ticket for repairing a cracked diaphragm.
Here's a link to the loctite oring kit and if interested you can read and see how it''s done with the Loctite 406.