Have you tried "Shooters" on University west? I used to deal with them when I was at NAS Jax.
They're supposed to have Gunsmiths and they sell trigicon night sights, so if you buy from them and they screw up the installation, they shouldn't balk at making it good. I would not buy off the net and ask them to install something that they could have sold you.
Call a few of the LGSs and see who sells and installs.
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