Hey.. I've seen old single-shot shotguns like this before that are actually in worse condition that what you have got that hadn't been buried for 7 years! This is absolutely a doable project. You are correct that many, many guns like this were made by Crescent Arms and labled for lots of various stores and such. Therefore, I think I would start by looking around gun shows, flea markets, auctions and the such for old guns like this, and try and see if there are any parts, pieces, or junkers out there that have the same latchwork for the fore-end and a matching stock. Many gunshows I attend have vendors who specialize in exactly this type of thing. If they don't have what you need, they will usually be happy to refer you to someone else who may be able to help.
P.S. have you tried
www.GunPartsCorp.com ? It's amazing what those folks have...
This may not be easy, but it's sure gonna get you out of the house, and you'll get to meet new people. By the way, you mentioned Davis in your original post. I sold a buttstock from an old N.R. Davis double years ago ,and have actually lived to regret it. Also, the finish on the receiver of your gun was probably color-case hardened originally.