You wont find anything that will that has any type of back piece that covers the back end of the lower. The design of the rear of the upper prevents that.
Your best bet is to select something that has no back piece that goes on the lower. Something like this. Except this is a right hand grip.
http://www.airsoftparts.ca/store2/in...roducts_id=405
However with slight modding to the upper or to the grip itself it should be able to fit.