I also designed the 3D-printed box for this project. You can find the 3D print files in the GitHub repository.
Please note that it is important to have a 120 ohm resistor between the CAN high and CAN low wires. If you do not have 120 ohm resistor you can manage to get that resistance using multiple resistors (100+10+10 or 60+60) connected serially. This is important because of the fact that CAN bus is intended to implemented by a twisted pair of wires, the transmission line impedance of unspecified twisted pair isn't exact, but 120 Ω is going to be close most of the time for the relatively large wires commonly used for CAN.
If you more interested in knowing this in theory, you can read about it Transmission Line Theory.