If you want to reapply a clear coat, FWIW I find that lacquer works well. It's essentially indistinguishable from the bare polished chrome. I use Mohawk Tone finish clear gloss because I have some. Its a professional touch up lacquer. I'm not sure if consumer level lacquer will work as well, but it might be OK.

My PX10 came with clear coated chrome. It didn't have even a spot of rust on it after nearly 50 years, though the painted parts were pretty rough. That convinced me to reapply.