If you just need the information they contain, and not a paper version, there is a very good source in New Zealand who I can thoroughly recommend.
www.flight-manuals-on cd.com Ltd whose postal address is P.O.Box 38-947, Wellington.
There are some sites who are less than satisfactory according to an unhappy purchaser who writes: Anyone interested in ordering aircraft manuals online should beware of eFlightManuals.com. I ordered several manuals from them in the past. You need a key to open them in acrobat but what they don't tell you is that after 2 years, the key expires. I've sent them several civilized e-mails asking them if I can renew them but I have received no replies. I spent a $100 on manuals that I can no longer use. It's very frustrating.