I replaced both pumps on my motor, and i got them from a company called Ebasicpower.com they have the best price for those pumps. i shopped around and nobody could beat their price. the pumps are made by carter which is the OEM supplier to volvo and mercruiser. i hope this hepls.
Try NAPA. If you know the part number you can go to there website and use ther parts lookup and see if they carry it. I know they carry the one for my boat, and its the marine version too.
napaonline.com the only problem i had with napa is sometimes they cost more than the oem from volvo
I picked up a new MerCruiser one at my dealer. It was a few bucks more but I knew it would fit perfect + if I had any issues I was able to go back to the dealer.