+1 on the Spikes 9mm Billet Upper. I too wish they still made this. I was able to procure one, but its cerakoted and has a few dings. I mounted it to a LWD G9 lower. Its currently in jail, so no feedback at this time. Its a super tight fit. I read somewhere that its in the plans to redesign one using the lines of the current Spikes Gen 2 billet uppers, but havent seen any developments on this.
Here are a few suggestions:
American Spirit Arms
9mm Side Charger
http://www.americanspiritarms.com/upper-receivers/asa-ar-15-9mm-side-charger-upper-receiver-with-modified-carrier-gen-ii
-i mounted this onto DDLES G9 lower. its a tight fit. the side charger hits the bolt release just slightly when racking to the rear, and the catch doesnt always keep the bolt back. I have not taken to the range yet. I chose this because the side charger is stationary and folds in during operation. Great company to also deal with.
Gibbz Arms
Side Charger
http://shop.gibbzarms.com/G4-Side-Charging-Upper-Receiver-G4UR.htm
-no experience with them. Saw them listed on the Quarter Circle 10 website as compatible with their lowers
X Products
side charger
http://www.xproducts.com/x-15-scu-side-charging-ar-upper
-no experience with them. Saw them listed on the Quarter Circle 10 website as compatible with their lowers