Chiappa makes a number of them, they generally have a shorter LOP than a lot of tac shotguns - including the Mossberg SPX.
The SPX has a 18.5" barrel and 39.5 OAL, the Chiappa has a model that has a 22" barrel and 39" OAL
They also make a 5-shot pistol grip only 1887 T-series with an 18.5" barrel, 28.6" OAL... it's pretty darn close to a Serbu
I'm not sure how you work a lever action when you don't have a stock pressed up against your shoulder... I would think that if you were just holding the forestock with your left hand, the gun would point to the sky when you worked that lever... I'll have to review old reruns of "The Rifleman" I'm sure Chuck Connors demonstrates the technique somewhere...
If that system works, I can really see that as a big hit with liquor store, gas station owners...