Many Raymarine plotters such as the C and E series use a now obsolete NMEA connector.
I tried for several days to source the 5 pin plug for NMEA without success, and can cost upwards of £60 second hand. In the end the nearest I could find was the following connector.
MULTICOMP CIRCULAR CONN PLUG 5POS CABLE - 2CT3032-W05300 (Fnl)
The pins are the right spacing but the keyway is 90 degrees out. It was easy to make a new keyway with a needle file and block up the original with a small piece of plastic and glue. Total cost £8. They are available on ebay or many other sites.
Original Raymarine Connector
This tip was originally submitted as part of a Raymarine GPS thread which can be viewed at: Jeanneau Owners Forum
Mick Bond - Fleur of Pendle - SO35