12V 2.3Ah Replacement Battery For Power Kingdom PS2.3-12 - (2 Pack)
Amazon.com: Rome Tech Replacement CMOS Battery for Sony Playstation 2/3 - PS2 PS3 Backup RTC BIOS Battery - 2 Wire Cable (2-Pack) : Video Games
Amazon.com: Rome Tech Replacement CMOS Battery for Sony Playstation 2/3 - PS2 PS3 Backup RTC BIOS Battery - 2 Wire Cable (1-Pack) : Video Games
Genuine Sony Playstation 2/ Ps2 Car Battery Adaptor DCC-FX160 VIDEO GAMES | eBay
⋆ CMOS Battery for PlayStation 2 ⋆ PS2 Clock Battery ⋆ PS2 CMOS Batteries - Rome Tech
Synergy Digital Power Tool Battery, Compatible with Atlas Copco PS2.4 Power Tool, (Ni-MH, 2.4V, 3300mAh) Ultra High Capacity, Replacement for AEG P2.4, PS2.4, PSX2.4 Battery - Walmart.com
Turns out it's not so easy to replace a ps2 battery. : r/ps2