G&R Tactical regularly has Colt products and seems to have AR15A4's in stock.
Colt AR15A4 - http://www.gandrtactical.com/cgi-bin/co ... key=AR15A4
Now just make sure your FFL doesn't have outrageous transfer fees. I've been seeing transfer fees up to $60 in certain places, probably people looking to cash in during election time.