So, you are likely to have literally dozens of devices that have a 'reset' hole in their case, perhaps it's a game controller, or that hole to release a CD from the old CD Rom that you don't even have a way to power it up, release the Sim Card and uSD card drawer on your cell phone. In my case I have about a dozen door sensors, motion sensors, and the like that if they lose contact with the home automation platform, they require punching the button behind that little pin hole. And a "pin" is probably not what you need. If you have held onto the drawer eject key that came with your cell phone, you're a better curator of that than I, congratulations. As for me, a paper clip is often the best option I can find. (Ever noticed how similar to a paper clip those drawer release pins for the cell phone are? Perhaps this can be modified or remixed for that?
In any case we don't have a lot of paperclips lying around the house either, so that's a slightly sketchy solution. But I do find them from time to time. In order to make it more comfortable to hold onto and use, and to make it a bit easier to find, and perhaps hang on a lanyard for when I might need to go around to a bunch of automation devices again, I designed up and printed one of these. If you have handy a pair of Countersunk M3 8mm long screws (4mm should work, but...) that is what the holes for securing the two halves together. I don't have those, so I grabbed a pair of socket head M3 8mm bolts, and that does a good job.
In the images, I show assembling one of these in grey filament along with an assembled black printed one. The black printed one on a key ring with a fob to attach it to a seatbelt buckle key organizer (That's not my design, I say go get that and use it too, it's handy.
I printed this at 100% infill, with a 0.08mm layer height in pla. no support.
For designing this, since I didn't want to design two mirrored parts and have to manage them on the printer, I designed it as one piece with a tab between them. That breaks off and cleans up with a pocket knife or deburring tool.