2000 Jaguar XJR

I have a cutomers Jaguar xjr supercharged in with a trans fluid leak. It looks like it is coming from a wiring bulkhead going into the trans by the bell housing. The local dealer says that they sell no parts for this trans, just reman units. This seems exorbitant to me just to repair a slight leak caused bt a faulty o-ring. Any help that anyone can provide would be greatly appreciated.