Yes! I purchased a set of bright "fluorescent" yellow stick-on PVC letter/number/symbol labels about 5 years ago because the original markings on the keys of our expensive ergonomic keyboard had mostly worn off. The stickers have been EXCELLENT! Completely solved the problem. All stickers have lasted intact and are as bright as when brand new. The keys are quite visible in even very low light. Highly recommended. Just be careful to follow directions about thoroughly cleaning the key tops prior to applying to guarantee they'll stick well. There are many brands to choose from on Amazon, priced about $6-8.
Now, if only I could still see the monitor screen clearly for more than 5 minutes...