Lightweight, but durable, Eheim EZ clips for Eheim canister filters are the hard-to-find part you're looking for.
Each clip easily snaps into place on your filter system, creating a proper watertight seal with the motor head and the plastic canister. Broken clips should be replaced immediately. Even one cracked clip can cause undesirable leaking.
Clips fit Eheim canister models 2226-2229/2326-2329/2026/2028/2126/2128.