Power-Sonic PS-1229 Battery, Sealed Lead-Acid, 12V, 2.9 Ah
This is the perfect battery for a "portable" system including a GPS only, or Pocket PC only.  I don't recommend it for a system with both a GPS and Pocket PC. 
Connectors: "FASTON" quick disconnect tabs (0.187" x 0.020"), mate with AMP. INC. FASTON "187".  See the AMP-FASTON-187.
Dimensions: 
Length: 7.01 inches (178 mm) 
Width: 1.38 inches (35 mm) 
Height" 2.38 inches (61 mm) 
Height over Terminals: 2.60 inches (66 mm) 
Approximate Weight: 2.60 pounds (1.18 kg)

Charging
Cycle Applications: Limit initial current to 900mA. Charge until battery voltage (under charge) reaches 14.40 to 14.70 volts at 68º F (20º C). Hold at 14.40 to 14.70 volts until current drops to approximately 29mA. Battery is fully charged under these conditions, and charger should either be disconnected or switched to "float" voltage.
"Float" or "Stand-by Service": Hold battery across constant voltage source of 13.50 to 13.80 volts continuously. When held at this voltage, the battery will seek its own current level and maintain itself in a fully charged condition.

Data Sheet: ps-1229.pdf