Hagen is discontinuing that line of canisters, it may be tough to find parts. Call around, you may find a LFS that has them, and check eBay as well. If you can't find replacement parts, you may be able to find an entire canister for a really good price - I work(ed, just gave in my notice) at a LFS, we're selling off the old line for 60% off to make room for the new shipment.