You can easily build your own. I have a dedicated Black Creek Precision lower (Colt mag) with a RRA upper. It has a bolt hold open. Works great. My 160 gr RN cast 9mm load is very accurate in it. The Metalform and ASC mags work, and the ProMags with a little tweaking work fine also. I have had a number of PCC over the years and the AR style is the best IMHO. I get about 200 to 300 fps more from the carbine over the pistol with high speed loads. The CorBon 115 gr load goes 1515 fps. Most of the standard 124 gr HP loads are right at 1300 fps.
Check over on AR15.com for info on building one.
Glock mag lowers are also available.