Try McDonnel marine in the east. Paul will ship you anything you need usually coming straight from Volvo. 860-243-9114. They are very easy to work with. Will give advice for free and one time even loaned me some tools (shipped them to me from CT, with that move they earned my business forever).
I've also used-http://www.marinepartsexpress.com:8080/empress/servlet/Impart?level=two&ID=2 When Mc Donnel Marine was on vacation.
You won't find cheap parts anywhere but if you do let me know. You can find equivalents from the truck/automotive side (filters primarily) but be careful.