2006-2007 is all LBZ unless you're looking for an LMM out of a newer body style 2007. They can be had on eBay for anywhere from $1500 to $6000 or so, depending on condition, included items, shipping, etc. If you want a brand new one, you're SOL unless you're willing to spend that $12-15K. Wrecking yards and salvage auctions will usually have decent deals if you can find a vehicle with a Duramax. If you had some talent, you could take a bare block and work from there. I believe just about everything else you could pick up from the aftermarket or the dealer, or even make yourself...might take a little longer though.
Later
Chris