Gun question for a friend who had a stroke

Here is the situation, at 22 years old a friend of mine had a stroke. After the stroke, he has very limited use of his right side. He is able to walk with a brace and has movement from the shoulder but has a brace on the elbow and has no use of his hand on the right side.
This year, he has been out with some friends duck hunting and found out he loves it.
He wants to buy his own shotgun. It needs to be left handed, pistol grip, and semi-automatic. He has been using a friends and basically shooting one handed with a pistol grip.
Can a shotgun with these parameters be bought off the shelf? I know they are looking at trying to find something in the $500 range, is this possible?
Thanks for any help you could offer

Mossberg makes the 935 magnum auto loader thats in the pistol grip. I have never shot one but looks like a decent gun, it should be around that price range

I second this!! My friend has one for turkeys and he is a big fan. Mossberg makes a pretty good gun for waterfowl, nice and simple with plenty of bang for the buck. They will last forever too.
You could always go remington route and add a pistol grip stock. I think the remingtons and mossbergs will offer the most “after market” stock solutions, no matter the gun you buy. That being said, when I gun hunt, I use a mossberg for everything from upland to deer.

http://www.cheaperthandirt.com/47813-55.html
This is without the pistol grip, but I imagine you could fine one for it.

http://www.mcgowanfirearms.com/mossberg935gtmagnumturkey-grandslamseries-pistolgrip.aspx

With pistol grip, and camo..about $250 more.
You guys could all pitch in a few bucks, sounds like its for a heck of a good cause?