What Raymarine/Flir does is they offer a "repair price" for newer models to replace what you send in. That is a substantial discount vs. the best prices available for new, and may be a better deal than someone's obsolete eBay part. OTOH it might require more installation work and/or replacement of related components, or addition of SeaTalk to SeaTalkNG converters. Not really a big deal, if you ask me. SeaTalkNG is also easy to interface to NMEA2000, which adds all kinds of options for integrating with other systems.

Maybe it's time to replace the old stuff anyway, for new. It improves the value of the boat at the same time.