We have tried several models and makers and are now using the TIM-LP from ublox and its Smart Antenna Module version, the SAM-LS. It has a low power consumption, 16 channels, 4Hz position update rate. The dynamic model is configurable. It uses the efficient UBX protocol and can provide positions in UTM.
The TIM-LP alone is 25mm*25mm and weights 3g.
The connector is a 20 pins FFC (Flat Flexible Cable) 0.5mm pitch. I had a hard time finding the cable and matching connector. I finally got them from digikey.