improvised stop
There is/was a YouTube video showing improvised "zero stops" by using a PVC pipe fitting and cutting it to length. I've done it and it worked for me on a Bushnell Elite fixed 10x. The PVC tube acts as a spacer and only allows the the knob to crank down to the zero you establish.
I can't exactly advise what fitting or diameter used, but the arrangement fit tidy like beneath the target/varmint turret. I had to cut a couple to get it where I wanted it, but once I got it, the arrangement has worked fine.
Essentially works thus: Set the elevation to the desired zero setting. Loosenen the screw holding the elevation knob in place, and removes the knob carefully without adding any clicks. To do this one must keep the elevation knob from turning as the screw is loosened and removed. Place the PVC fitting inside the elevation knob, and set the knob with insert, on top of the elevation turret and rethread the screw that attatches same. The screw should snug up, with the knob resting on top of the insert you fashioned.
Look for the video, best I can do in print.