Depends what you want done. If it is just a logo or something like that you can likely find a local place that can do a good job. If you are looking to have the whole gun engraved with scroll pattern or something like that, then forget the laser engraving. They are fine on flat surfaces. Some of the machines can engrave on a straight cylinder. Machine rotates the item being engraved. Problem is that the laser has to focus. That means it must remain at a fixed distance. A non fluted cylinder works fine. Not so much for a fluted one. You can engrave side of the barrel, but if the design goes onto the barrel lug also, you have problems. Back of recoil shield and back strap are not going to work well. It will work fine on the side plate.
Laser engraving is fine for logos, but even at its best it is terrible for any kind of artistic work. Most laser engraving just burns a chemical onto the surface of the metal. The good laser engraving actually removes some metal. Problem with laser engraving is will never be mistaken for real engraving. It is as obvious as you can get. Sort of like spending $20 on a fake Rolex then trying to act like a bigshot. Even a lousy hand engraving job beats the best laser engraving job. Full coverage hand engraving is going to start at several thousand dollars. If you want something sculpted or with some bulino work, get a second mortgage on your house.