OEM Garmin GPS from
Ryda for $92 Aust.
Just make up the appropriate cables for it to get pwr (from Gemini) & plug into the Gemini. Or just get the Serial version.
I guess (with this version receiver...the LVC) you could even make a serial connector adaptor for it was well & use it on a computer serial port as well.
Or even cheaper...
Ebay. $USD though.