I was going to order one from Bud's Gunshop online - they have them advertised for $99. I usually get my FFL transfers through Green Mountain Guns - they charge $25 for the transfer. Green Mountain has stripped DPMS receivers for $129 so I figured I couldn't go wrong with the DPMS...cheaper after shipping.

They also have stripped Bushmaster lowers in 5.56 (.223) and .308 but I don't remember the price. They have some complete lowers in both collapsable and fixed stock configurations as well.

I say buy one and give it a shot - I don't think you can go wrong on a stripped lower.