Voltage: 3.7
Capacity: 2200mAh
Type: Lithium Ion (Li-Ion)
Charge Cycles: ?
Charge Time: ?
Connections/Plugs: ?

Messurments taken at the shortest points to work out what size cell is inside.
Length: 69mm
Diamter: 20.5mm

We are only taking a guess at what cell is inside.
From the size of the outer case it could be a GP1865L220
It's size is right at 18.3mm x 65.2mm
It's capacity is right at 2200mAh
GP datasheet can be found here in PDF format.

Apex Digital Currently the only known place to sell batteries for the unit online.

Manufacture: Gold Peak
Manufacture Website(s): Gold Peak / GP batteries SG / GP batteries / GP batteries HK

Possibly has a 3/2 AA standard lithium Ion cell inside the plastic case.

I have heard that this same battery pack is used in some camera's.