When the cheap and flimsy hook that came with my Aiper Scuba SE broke, I realized it would be super easy to design and print one that is much sturdier. I designed it in two parts so the pool orientation is vertical and the hook is printed on its side. I used triangle pins to align the two pieces and just used super glue to attach them (you can see a little bit of yellowing from the super glue accelerator I sprayed on the white PETG).

I recommend using PETG or something else that can withstand sun and water/chemicals. I've used this for a few weeks now and it is far stronger than the original hook that came with the pool robot. Since I'm not great with CAD programs yet, I just designed the entire thing in Prusa Slicer with Add Part and Add Negative Volume. I'm sure there are better/simpler ways to do this, but this worked for me. :)