Not sure what your definition of “TIGHT budget” is… I just picked up a Manker E02 that’s red and you can get it with Nichia 219c, too. It’s around $23. Quality is good. Moonlight mode is programmable.

However, it does have a magnetic tail. To me, that’s a plus, but if you are truly planning to use it as a keychain light, then it might just be a hindrance.

Or did you mean red as in red beam?