Here's one I don't know anything about ...but in AR at least....
http://www.gun-parts.com/stocks/
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Here is one that some of my buddies have used and I would recommend ....on the high end / but very good work. But nice high end wood - is expensive. Average stock for a shotgun is probably $2,500 ..../ but you can easily get up to $5K or more....depending on what you want.
http://www.gunshopfinder.com/bytownresults.asp?ID=4103
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What's your budget --- or what are you trying to do / on what kind of gun ?