I constructed this out of pvc pipe, a couple pvc couplings and a wood plank.
Traced my shotgun stock and slide, cut it out with a scroll saw, sanded smooth.
Screwed a notched piece of 3/4 in pvc pipe to it.
Used 2-1 in pvc couplings and screwed slide to them.
Used screws in pvc pipe to limit slide and make cocking noise and one set screw which I kept tightening as a slid the slide to create a shallow groove to keep the slide in-line.
I had all the components, so cost me zero to make, just a project I did to keep hand in correct placement of my real gun while performing a shotgun cocking action, barrel is shorter, but wasn't a need for that to be exact, just where the slide fell for the hand reach.