Why not just get a "”conventional” hand-held GPS
, which can be used in the dingy, or for walking, since they have their own small display, buttons, etc?
They will at least display your lat/lon location, and may include many other features - depending on the software
contained inside. Examples include the lower cost Garmin
models like GPS12, GPS12XL and Etrex, or the 310 or 315 from Magellan
. Many of these have a NMEA interface
and an optional interface cable.