If it is a set of steel barrels, my first call would be to Giacomo Sports in New York (315-336-1356). These are ex-Perazzi people who specialize in Perazzis and other high end guns, and are renowned for fast, compotent service. I have heard of guys getting a barrel set back within the week if needed, but in no case will you be without for as much as a month. If the tubes are damascus, Kirk Merrington in Texas (830-367-2937) seems to be the odds-on favorite at least for authentic refinishing, and he could probably get you started in the right place for getting the rib relayed. Those are just two quick suggestions. I have no doubt there are others out there that do excellent work also.
Don't let people talk you into thinking you can do it yourself by rubbing some sandpaper under the rib and tickling it with a soldering gun or, worse, sticking some epoxy down there.