No idea if they take paypal but just for reference
Link
Look for the more mAh - bigger the number , generally lasts longer
Then you need a charger
Link
Most tend to be mains ones, but there are some in-car ones too
some come with batts too, again look for a big mAh number
Not a bad option here
link main s + 12v car charging + 2700 bats x 4