Briley has a large selection of outside diameters that they can chose from to match to your gun's dimensions. They also have the broadest experience, having done more guns than others. That being said, they are also among the most expensive.

Local small smiths can probably do your job for more than a hundred dollars cheaper than Briley. I've heard good about Bob Day in Pico Rivera, CA and Mike Orlen in Amhearst, Mass. I had some work done by AnglePort that I was happy with as well.