My son is off on an adventure with his GoPro Hero 7 and needed to remove the lens cap often, this seems to be a difficult task with wet slippery hands so he asked if I could 3D print him a "spanner".
This is my solution, it should be reasonably robust and should not slip and easy to store in a pocket or such.
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/7o40TUxnip1
I used a 0.1 layer but I don't think 0.2 would be detrimental.