Screw a Thorlabs AM45T angle mount onto each of the Thorlabs TR2 posts and insert them into the two mirror mounts in the breadboard.

Laser cut one copy of the mirror file out of 1/8 inch mirror acrylic. Be sure to laser cut with the mirror side facing down!

Use any 8-32 screws to mount the mirror on the angled mounts. The mirror's sharp corners should sit inside the wheel as far back as possible (towards the spoke) to maximize the surface area of the wheel reflected in the mirror. However, make sure the mirror is not pressing on the spoke and inhibiting the wheel's motion.

Polycarbonate is strong and transparent, but also very slippery! To solve this problem you can put a layer of PDMS or other transparent silicone on top of the wheel to make sure your mice feel comfortable and can run quickly. You can also laser cut a track pattern into the PDMS to allow further traction. To do this:

Cut the track file out of a piece of thin PDMS. Then place it over the wheel and tape at its junction.