n-o-d-e has what he calls a data runner mod which includes simply swapping the stock green light with a brighter white one. I’ve had one for years now, and its still not ideal, but definitely better than the original:

https://n-o-d-e.net/datarunner.html

There is one, but requires another Casio watch to borrow the backlight from.

https://youtu.be/9-jd_7eXACU

You can buy replacement backlight spreaders off of etsy. I did it to mine and the backlight is now usable..

There are some diffuser mods available too that look like they would make a big difference.

Buy a W-86-1VQES instead.