Those older Wingmasters are great guns... depending on how they've been used (and if it's been modified...). Yes, there are plenty of different barrels around for them (and each shotgun is a different proposition - solely dependent on barrel length and the choke that it comes with..). Many, many of those old shotguns, particularly ones with short barrels (between 18 1/2 and 20") actually never saw much use - but a lot of them, if ex-police guns, did get beaten up a lot rattling around in one cruiser or other...
If you're looking at a Wingmaster with a nice looking well finished stock with good checkering at grip points the odds are that it didn't come with that short barrel when new... If the barrel is a factory short barrel no problem - but many have been cut down by someone to a shorter length - and those I'd want a gunsmith to look at closely before making a purchase if possible. Remember that it's not legal to have a shotgun with a barrel that's shorter than 18" (that's why most only cut them to 18 1/2" to be on the safe side...) unless you've paid an extra $200 for a federal ticket (go to ATF for all you ever wanted to know about that topic, unfortunately). Remember as well that the measurement is from the bolt face to the muzzle (stick a dowel down the barrel until it stops at the bolt face then mark the dowel at the muzzle, withdraw and measure carefully..).
If the shotgun has a plain jane stock with an oil finish and no checkering it might be a police model (older Wingmasters never had a single marking indicating that, but the cheaper stock is a dead giveaway...). Make a point of going to Gunbroker.com and searching for "Remington Wingmaster 12" as part of your efforts.... There you will find more than a few short barreled Wingmasters - both cut-down guns and former police models... You'll also see a pretty good range of prices (this past year they've gotten much more expensive than they were just two years ago... ).
Good luck and let us know what you purchase. That old Wingmaster was in my hands on every hot call for years in police work.. Today I have it's modern equivalent an Express model with synthetic stock... It's still my first choice for close quarters work...
Here's an example on Gunbroker right now of an ex-police Wingmaster if I'm not mistaken... It has everything I'd be looking for (although I prefer an improved cylinder barrel.. but that's just me...)
https://www.gunbroker.com/item/903564633
If you call up that auction item please note that it does not have the trigger group or the pins to install it... That might have something to do with zero bids at present. If it were me I'd price out the needed items elsewhere, make sure they're available - before making that first bid...
Here's an outfit that will either have the needed items or know where to get them....
https://tacticalgunslings.com/