....sure I have one, 5€ plus shipping in an envelope to your place. Anyhow, let's try to figure out first why your's is not staying in place. Might need some bending somewhere?
I was thinking the same thing; it's a basic part, with a pin (hook) on one end and a snaplock on the other side. The cable runs under it, being pressed down. The 'floating' lip in the middle of the clamp has 2 teeth that bite into the cable, preventing it (if all is well) to slide back and forth.
These parts are all present in the pic you share, so it leeds me to believe your part may be deformed, or the cable is (locally?) thinner.
As a simple solution; would it not help if you put one or more zip-tie(s) around the cable, e.g. one just next to the teeth, and one on either side of the clamp?
Possibly even another, running under the cable, and crossing over the teeth?
As there are 8 of these clamps on the heater control mechanism; (one on either side of the cable, 4 cables).
Does the problem 'move' if you switch 2 clamps? This test would confirm if the problem indeed lies in the clamp - possibly it could be loose on the other side as well.