Your search for "PA-BT-002" revealed the following:
Brother PA-BT-002 Li-Ion Rechargeable Battery
$198.00For PJ-700 PocketJet 7 or PJ-800 PocketJet 8 Series Printers 600 Pages per Charge PJ7 Li-ion Battery: Rechargeable, 1750mAh, 10.8VDC, 19Wh...