The places I see engraved guns is at gun shows. Big ones particularly. Keep in mind that if you're out of state, you have a minor problem figuring out how to comply with laws. But also realize that engraved guns usually don't sell the first time a vendor brings them along. Some languish for months or even years. It provides the opportunity for you to negotiate and solve the payment problems. Remember, almost no one wants to take a check from someone they've never seen before. But you can pay by check and then if you trust the seller, have him ship it to your local gun shop.
My story about meeting my longtime gun show partner: Some old coot (John) had a gun on his table that I really wanted badly. It was a ratty old M57 with factory engraving. He wanted $2400 for it. I'd been seeing it on his table for a bunch of shows. We'd engaged in some friendly banter, with me offering $2000 and him not coming off his price one cent. There used to be 5 big shows put on by National Gun Day. He was set up at every one. I never missed one either. Same negotiation, no changes. We'd even become friends over the years. Every show I'd show up and it would start.
So the one show in the Mid 1990s I was dragging along, having walked the entire show. Before I could present myself, he started in on me from a few tables away. Things like when am I going to pay a fair price and not just be a looker. By then the entire island of tables was watching and laughing. So when I walked the last few feet and put down my bag, I smiled at him and said "I'll pay a fair price when you offer me one". Again laughter from the peanut gallery. Because this scenario in some variation had been taking place for so long, I figured it was time to change the dialogue. So I reached into my zipper pocket and pulled out my stash. On the glass top of his display, I put 20 Ben Franklins. I'd even practiced the art of spreading them out, fan shaped. He was in shock. And all the other vendors in the island were in hysterics. Its called "calling his bluff". It worked, too.
I have a K22 that we think was engraved by Ben Shostle. No way I'd have bought it if I hadn't handled it first. Seeing the gun you want in person is much better than trusting how it will turn out. I know the theme of this thread is factory work. Its consistently good. But independent engravers do sometimes better work. My conclusion is that you can depend on the factory, but if you want a really exceptional piece, you can do better. And less expensive if its already engraved.
Keep in mind that usually the amount you pay for the gun and then for the engraving ends up as more than the engraved piece is worth. The only reason to commission engraving is because you want some unusual and specific thing. If you are willing to settle for just a really attractive gun, save yourself some money and buy one already done where you can see the results.