The pin on my decomp control broke as well, probably while maneuvering the bike to park it . With the sidecar and steering damper there is a lot of pushing and pulling to parallel park especially on a hill.
I was going to replace the plastic pin with a steel one but there was not enough material to drill and epoxy to. I took some 400 grit wet / dry sandpaper, folded it grit side out and slipped it in between the handlebar and switch. It is working so far, then again in the long run all solutions are temporary. Don