JtinIN
Well you have several options, ASA, Olympic Arms and Colt make some. What setup do you want? If you like the Colt setup I would recommend the Rock River option. Colt uppers are expensive and hard to find. RRA is a copy of Colt.
The Oly system is what I have. I went with the A2 upper since I knew that I would not want to invest money in putting optics on a 9mm. I have the First Samco M44 handguards and pistol grip. I do plan on putting a light on it and that's about it. It is a plinker gun and I use it to shoot a indoor pistol ranges if the weather is not cooperating.
Enought about my trash. I hope this answers your question.
Max