Ah!!!! It is a slippery slope you are looking down on, but one that can bring more than a few great times.
The Urgartechea is a great shotgun in a box lock. The Grade 1 starts out more than what you are looking to spend, but used is another story. And there is a lifetime of solid use in one of these. Bookmark "Lion Country Supply" and keep checking their used ones and eventually one will show up. Not sure if you would prefer a straight stock or not, and they take a bit of getting used to. They may make them with a pistol grip, but Im not sure. LCS could answer that question for you.
Friend bought one a few years back. Has used it hard and shoots it better than good on Grouse.
http://www.doubleshotguns.com/ugartecheagrade1boxlock1.html 
