I have modified Blasterforge's #2 Stock to fit a Nerf Retaliator or other springer type blasters. The top of the stock is cut to follow the contours of the Retaliator. There is a hole on the top that aligns with a top rail that I designed. You will need an M4 screw to secure the two pieces together.
I printed the part with no supports in the vertical position. You should be able to do the same with the stock end. I printed the support bar (which is optional) and stretched it by 20 mm. Resolution is 0.2 mm layers with three wall layers giving it a total wall thickness of 1.2 mm.
Retaliator Picatinny Top Rail: https://www.thingiverse.com/thing:3064900