>>1812784>>1812786It's not circular, it's oval-ish.
The upper part should be the strongest, in theory, so I thought 2 small holes if well centered wouldn't do too much damage.
I went around decathlon (the only sports shop around here) and every water bottle holder I saw needed screws to mount, I guess I'll try looking on amazon to see if there's something that looks like it'll hold with zipties.