I looked into this extensively during lockdowns. There is a specific wavelength that maximises Vitamin D. And there are medically approved devices that use special fluorescent bulbs that output this. It's mainly used in Nordic countries.

I tried to find an LED strip equivalent but couldn't not - there are strips that produce a lower wavelength than UV-A but from what I remember it was too low of a nm for good vitamin D.

Could be an interesting product however ! I wanted to hand two strips in my shower and turn them on for a few minutes while I washed up during the winter.

Unfortunately even the tanning beds you were using still produce a lot of UV-A which will age your skin. And funnily enough UV-B also produces a much longer lasting tan (though slower) which would mean less return trips for people who are just looking for aesthetics