Honestly, momentary switches are the simplest of all circuits. The only hard part will be soldering a new one into the old leads. What laptop is it? I can look and see what I think.
I did a quick look and it doesn’t look like the switch is directly on the motherboard so most likely there’s a JST plug or something similar with wire leads that then hook into the switch and/or a daughter board. If it’s just two wires into a JST plug you can replace the switch with anything similar or if you wanna be ghetto about it just touch the two wires together to make a short.
You can probably get the exact switch if you look hard enough since almost everything but the exterior shell will be commodity components.
Good luck!