This is a simple mod to make the light from the NERF Recon fit the NERF Stampede.

Step 1: Cutcutcut

Cut along the red lines. You can use a Dremel cut off wheel, leaving a small amount of extra plastic. Then use some fine sandpaper mounted to a flat surface to get the edges flat and matching eachother.

Step 2: Fitting the Battery Tray

You will also need to cut out a slot for the switch.
Glue the pieces back together. I used Weld-on solvent, but super glue would work, or even using a soldering iron to weld it.
Carve out the shell to fit the battery tray as shown.

Step 3: Battery Cover

The tactical rail clip will double as the battery cover. To do this, mark and drill a tiny hole on the skinny end slightly larger than the screw from the battery cover, then insert the screw. Be sure to put the tiny clear plastic washer back on it to, this helps to avoid losing the screw when you change batteries.
You will also need to file the overhang off on all but one of the sides of the clip, so it can come out easily.