Turns out it's not so easy to replace a ps2 battery. : r/ps2
Amazon.com : STK NP-FW50 Battery for Sony Alpha a6500 a5100 A7R II a6300 ILCE-6000L ILCE-6300 NEX-5 A7 a6000 A7sii a3000 A7 II ILCE-6500 NEX-7 DSC-RX10 III NEX-6 : Digital Camera Batteries :
If you own a PSP, you might want to uh, make sure your battery isn't expanding – Destructoid
Amazon.com: New Replacement Battery LIP1412 Compatible with Sony PSP GO PSP-N100 N1000 N1001 : Video Games
Pro Charging Systems PS2 Professional Battery Charger | Remy Battery
Amazon.com: OSTENT 3.7V 930mAh Rechargeable Battery Pack Replacement for Sony PSP GO PSP-N1000/N1001/N1002/N1003/N1004 : Video Games