I was on the CDNN Sports website and saw they have DPMS stripped A2 Upper Receivers for $39.99 (plus ten dollar flat rate shipping). This is a pretty cheap price from what I have seen lately. Limit 3 per person, at least when I ordered.
http://www.cdnnsports.com/ar15-upper-receiver-a2-stripped-fixed-carry-dpms.html
http://www.cdnnsports.com/ar15-upper-receiver-a2-stripped-fixed-carry-dpms.html