I have the CQC for my M&P45, which is the same one the G21 uses (this is the one I have...
http://www.midwayusa.com/eproductpage.exe/...&t=11082005 ). I also have the M&P9c, it does not fit the holster. Let me re-phrase that, the 9c will fit in the holster, however, the holster is much longer (due to barrel length) than the 9c. The retention and all works fine, just too long. If I get a chance I will get up some pics. I really like the Blackhawk Serpa, it is perfect for the 45 and my requirements.
Lots of good holster recommendations on the compact board, unfortunately I don't think any are Blackhawk...