fullcarbonbike

The only thing I can think of is, find a small plastic ball/bead that would fit into the hole (and not slip passed the switch). Then cut a small section of an old bicycle inner tube to go all of the way around the body of the ion 700, but just long/wide enough to cover the hole and keep the bead in place. That should allow you to press on the bump where the bead sticks out and the inner tube would keep it in place and prevent moisture from getting inside the ion 700.

I’m not familiar with that model. It seems like it’s laid out similar to the ion 700, but without any externally visible screws. Does it sound like there’s anything loose inside, if you take it off the bike and shake it? If you do hear something rattling around inside, you might try to remove the rubber cover over the on/off button (that cover was removable on the ion 700). It may give you access to a screw inside/under the cover, or if there’s a part broken it might come out through that area. A loose part inside might be shorting out the on/off switch. That's about the best I can suggest. Good luck with it.

The replacement battery will be 4 years old on Oct. 1st 2021, it's still working, and lasts through several rides before needing a recharge.