The short and easy answer is a Garmin GPS
76....(I own 4 of 'em, of various models and ages..!)
They work GREAT....
They work great below decks, and provide excellent NMEA
data output to radios...
I've been using a Gamin GPS
76 to provide GPS position data to both my Icom
M-602 VHF-DSC radio
and my Icom
M-802 HF-DSC radio
, for 9 years now....
I have the Garmin
optional adjustable mount and the "12vdc input and NMEA-output" cable...
See photos here....
s/v Annie Laurie