I think I have what you're looking for
I'll check the model but it worked perfectly except I wanted to tie into my new nmeawind ,depth and radar so I sprang for a new plotter too.
Pm me and I'll find out tomorrow what model it is
I have a Si-Tex Colormax wide it's very similar to the SH 300. It uses the same chart cards, I used this as a dedicated radar display until I updated to a cp590, still have the cp300i but plan on keeping it for awhile.