Where can I find a replacement pump for my Diplomat dishwasher ?

My dishwasher stopped working,it would fill with water but emptied again after about a minute without the re-circulating pump staring up.The upshot of my investigations revealed when testing the pump and motor on the bench that the coupling between motor and the plastic pump had sheared.The motor ran extremely smoothly, so I thought finding a replacement pump would be staightforward.Not so.Quite a few spares suppliers want to sell the whole unit complete ,which works out expensive when all that is needed is the plastic pump. So, if anyone knows of a supplier who can sell me the part for a Diplomat type 12033 Model ADP 8224 I would be extremely grateful.
Regards
Mike Cottam