I found one with a lot of gba games, I think it only works on a computer though
ultimate-games.github.io/gba
It’s blocked on my school computers, so I can’t check, but I think that the arrow keys are the directional buttons, z and x are a and b, and I remember I think 1,2,shift and enter did stuff too. It’s been a while since I’ve used it so I can’t check.