I know that it's a bit late now, but I don't think that many Rotax users realise that the Bing , Pierburg and Stromberg carburettors have a lot of component commonality , and the 912 rubber carb. diaphragms to which you refer are exactly the same as those in a Stromberg CD150. and widely available from classic car suppliers for about four quid.
And no , you don't have to "register" with them or give all your details to them, and then have to explain to them your suitability to be doing this sort of work , or elect yourself for an iRMT course .
I use Southern Carburettors at Gatwick , they have this weird procedure , you phone 'em , order your bits and give your card details ....... Can't see that ever catching on mind....
