This is an open source design by muphins that is available on Thingiverse.
”A stock for the NERF Roughcut blaster. it doesn't improve accuracy but looks cool.
The model is the left half, mirror it to have the other half.
Use M3 screws and/or glue to attach it, 2 M3 holes are present.
A little sanding may be required to adjust the thickness of the two halves to attach them tightly on the blaster.”