I don't know anyone who offers this service but it is something I have done myself and I know a bit about it.
If you find someone who will quote you a price, you should insist on seeing pictures of previous work done. Most people who polish guns go hog wild with the buffer and end up making it look like crap.
If done properly it takes a great deal of time and effort first sanding and then polishing with an eye to keeping any lines crisp and sharp.
A good article about polishing can be found here:
Choosing and using polishing tools
Some good quotes from the article:
There are as many ways to ruin a firearm through improper polishing techniques as there are firearms to ruin. Potential problems include rounded corners, dished screw holes, wavy barrels, dings and gouges that are not polished out, blueing over rust, letters and numbers pulled, and bead- or sandblasting used in an attempt to cover poor polishing techniques. The results? The destruction of firearm value.
Machine polishing has probably ruined more guns than it has saved. It is quicker than hand work, but much more care is required to do it correctly. Everyone seems to have a method of machine polishing that works best for them, and you’ll probably discover a technique that works best for you. Just remember that polishing wheels cut much more quickly than hand polishing, and can ruin your work before you realize what is happening.
