I think I made something like what you're describing years ago - I used two appropriate sized bits of plastic pipe about 3/4" wide and spaced 4 inches apart attached to a bit of wood shaped to fit the finder bracket. I just drilled and tapped three screws into each bit of plastic to hold and adjust the lazer - worked a treat but looked pretty agricultural. You can still buy them like this one
https://agenaastro.com/agena-laser-p...ixen-foot.html
I've had absolutely no trouble getting lazers off ebay that are marked as less than 1mw posted into Vic - which I think is the legal max. One or two of them are obviously a lot more than 1mw but I live out in the country and use them with care and discretion.
The biggest problem I have found is they often don't function well when they get cold - something to do with the frequencies shifting of the led's - I used to always think it was the batteries but it wasn't.
I use a red dot finder these days to avoid any fuss, but it was a very quick and easy way to point a telescope. Great to point things out to friends and family but if I'm going to a star party or public area, I leave them at home.