My mother kept breaking the hard plastic clips that came with the bag of her insulin pump. They would not sell the clips separately, so I made this model of it.

It is a 1-1 drawing of the original clip from Accu-Check.

Works fine when printed in PLA, which is already much more flexible than the original polycarbonate.
Any layer height works (I tried with 0.15 and 0.2). You might need to cut the opening free with a knife.