It would need to be fitted to the gun, as with any double with switch barrels, so it wouldn't be easy or cheap. Entirely unsure about the set of 12 gauge barrels, sorry, just chiming in to mention a smoke and fit would be required. Depending on the shotgun barrels, that may also mean building up some surfaces with TIG, then fitting, if you're unlucky. If BRNO offers a set, unfit, then that'd be easier as they'd be left tight. It's definitely a job for a true gunsmith, not a gun assembler. (I'm an assembler with some talent with files and stones, so take my opinion to follow with as much salt as you see fit) If you find a barrel set I'll be happy to point you in the right directions, but this would likely be a pricey project. To give you an idea where to start project consideration wise I would charge $1,000 for a straight smoke, fit, and finish match if a new tight set of barrels were found for reference. If the barrels required rehooking to be tight on face, and underlug build up, it would go up from there.
