Here is the shop I used. www.caylor-custom.com These guys do a lot of custom work. I told him that my pistol sights were dead-on perfect, so he measured everything before the installation of my night sights.......and they are dead on too. No tool marks were left by the install....great job. I don't remember what he charged. I waited while he worked, they have shooting videos to keep you entertained. I will also note that I am 99% sure that Mike Caylor is a certified HK armorer.
I think the Bullet Trap in Plano can do it too. You might call them.....(972) 881-0372