I found some clips like this one on thingiverse but they all did not fit. So I took the thing from WilliWichtig and redesigned it in most parts. Now it fits quite nicely and i do not fear that the baking tray would losen by itself.

I printed it "standing" on the side so it has the maximum stability. You will need a raft to get reasonal adhesion to the printbed (see pictures).