Check the Beretta 3901 RL Target - 12ga, reduced length buttstock, light recoiling semi-auto, adjustable comb, adjustable LOP w/spacers, shoots up to 3" shells. This is the gun my wife bought for herself. We (she) paid $875.00 out the door brand new.
Interesting suggestion, as it probably indeed would fit her without any gunsmithing. However, I've never seen one listed anywhere for under $900 Did you get your wife's gun a while back?
$900 might be a bit pricey for his budget, too.