You can order all Cannon parts from Fish 307.
https://www.fish307.com/cannon-mag-10-stx-ts-downrigger-parts/
Most of the Magnum downrigger parts are interchangeable. If you have an old board or relay, you can just switch out to a new one. I run Cannon downriggers (I have owned Scotty's as well), and they are very easy to work on. They are just a motor and a switch basically. The board simply allows the positive ion control and autostop to work .
Just to add a little additional input to the thread. I had a Scotty 2106 on one gunnel and a Cannon Digitroll 10 on another for a full season. I have always run Cannons but I was interested to compare the two side by side for a full season of fishing. I like to compare things like this and make sure that I am forming objective opinions on what products work best for me. As mentioned by previous posters, the Scotty customer service was great. I dealt with them many times over the course of the year that I ran the Scotty and was very pleased. I have never dealt with Cannon's customer service. I have Cannons on both gunnels now.