High contrast external keyboard?

Does anyone know if Apple makes an external keyboard for low vision users? I have an Apple keyboard that I use with my Mac, but I can barely distinguish the keys from the keyboard surface, and I can't read the individual key names at all.

Another approach would be to find high-contrast key caps to fit over the keys.

If Apple doesn't make high-contrast keyboards or key caps, can anyone recommend another vendor?

Thanks,
Kathy