This is a pretty specific Thing, but that's what 3D printing is for, right? Anyway, this is set up to print upside-down so the recess for the hex nut is on top of the print. As such, the cutout on the bottom may sag a bit when printing without support, but it didn't seem to be a problem in use.
I sized the hex for a specific 1/4-20 nut I had on hand, and am not sure if it's a standard hex size or not, so you might want to check that before printing. The bolt I used was a 1/4-20 x 1-3/8 SHCS which ended up being just the right length. a 1-1/2 long bolt would probably work as well.
My print snapped right into place on the Pan-Tilt rig without further modification, but it is pretty snug. When I did the design, I forgot about the issue with 3D printed holes being undersized, so I ended up chasing the through hole with a 1/4 drill on my initial print, but I've already adjusted the file a bit to compensate for that.
Also, the pic doesn't show it but I run the PiCam flat cable out the bottom of the camera and thread it through the pan-tilt rig in between the 2 servos. It seems to handle the motion well when routed this way.
Let me know if you have any problems with the files.