How to replace driver sun visor mirror

What year is your HR-V?

You're wanting to replace just the mirror glass, not the whole sun visor, is that right?

I can hope I'm wrong, but I'm skeptical you're going to find much information on that repair; most everyone is just going to go ahead and replace the complete sun visor, since nobody makes parts for a sun visor.

This guide should give you a pretty good idea about how to remove the sun visor; I suspect you'll have to take it out if you're really set on trying to disassemble it to replace the mirror glass.

Removal and Installation — 2022 Honda HR-V LX, FWD Service Manual ~ LEMON Manuals

I hope you're good at cutting glass, because otherwise I don't know how you're going to find a replacement piece of mirror glass outside of cutting your own.