There are two Wingmasters with plated lifters sitting in the Gander Mountain store in Spring, TX. (north of Houston) The store is at I45 and TX 2920. I was just there today but did not handle the guns. One looked like a 20 gauge. You might call them. I went on the GM web site and there is a 20 listed at $699.
Neither of the guns I saw had that high a price. Just an FYI...phone number is 281-288-2620.