I use a Polstar gps mouse it measures 4cm x 4cm, it's weatherproof and has a magnetic base that keeps it on your car. It supports nmea0183 v2.2 and works on all the APRS Kenwood models TM-D700. TM-D710, TH-D7 (apart from some early D7's). It requires a 5V supply (I used a 7805 regulator IC), and it gives a serial output easily feed to a kenwood.

Parts used:	Polstar GPS mouse 7805 regulator PS2 socket (to plug gps into) 2 x 0.1uf ceramic capacitors fuse holder & 250ma fuse
Handy Links:	Users Manual from Polstars website. Data sheet from Polstars website giving pinouts. How to build a 5V regulator using a 7805 (see figure 2) UK suppler of the gps mouse Click on GPS Receivers