I made this mount for my Ender 3 Neo (I'm assuming any Ender 3's would mount the same) so my blink camera can be held on using the Z-Axis Cross Bar Bolts. It mounts using the stock bolts that hold onto the tensioner pully. The image cannot be rotated 90° (this is a Blink issue) but it allows you to view the print as it goes keeping in line with the Z Height. I included the prt file as the fit is pretty tight. I wanted it to be snug so it wouldn't slip.

Printed with 15% infill on Elegoo PLA Filament and tree supports