Their 'custom shop' does them now. The Bass Pro Shop 'Fine Gun Rooms' are listing Skeet and Trap Superposed starting at a little over 2 grand US. Although one of 'em lists a Belgian made 12 ga at only $1799US. Then they go up. Way up. Seven grand US and up. It appears that the stock, guage, where it was made and other features determines the value. Just like any other firearm.
Know a guy who owns a BAR LMG that was made in the 20's for the civilian market. It's got the nicest burly walnut stock and the old S&W bluing, even on the mags. Prettiest MG I've ever seen.