Lisa at Troncali Subaru, Ryan at Irvine, and Pam at iSR Performance are all good sources for Genuine Subaru parts.
I've purchased the genuine parts from Pam before with good results. Lisa and Ryan will be receiving a call soon enough for a large order of gaskets. My dealership is charging double what subaruparts.com is charging.
Sometimes if you are really nice, you can get the dealership to pull the part numbers off their little VIN number part search. My dealership's service department had a field day with my transmission and because of that, I may be able to source various part numbers... I have all the shift linkage P/N's now