Nightforce is closed on Fridays so I tried the Hide. Turns out the pitch is 1/4-28, which appears to be pretty standard for a 1/2" nut. I ordered a set of TPS hex nuts from Midway. I was surprised that I couldn't find any Nightforce nuts. I will keep a few spares handy from now on.
Here is a link to the site that helped me determine the pitch: