Can't provide any assistance in your search, but do want to wish you good luck. When I bought my boat it also had older Nexus instruments on board. Some were in need of repair or replacement. In reaching out to all the global distributors, I found them repeating the same story: Since the Garmin
acquisition of Nexus, all old products had been discontinued and parts/equipment were sold until gone. Unless you're dealing with late-model Nexus instruments, made after the acquisition, I think you may find it (have already found it) really hard to get replacements
I ended up removing all the Nexus brand stuff and replacing with new instruments from a competing (and more accessible) brand.