I'm not intimately familiar with your particular model compressor, but I would expect that you could find what you need by going to www.aircondition.com. Once there, click on "straight to the board." At the top of that page is a box with four different links. One of them is auto ac parts and they have almost everything.
Typically when the compressor is leaking it is the shaft seal, but if the leak detector showed the leak at the manifold, then the o ring seals can very well be the culprit.
BTW. If you go to an auto a/c shop for this repair. They can recover and recycle any R12 that is still in the system. So unless it is bone dry, don't pay again for the R12 since they will reuse it.