You can find some PS3 controller batteries in Amazon or Ebay. Maybe this one might work for your PS3 controller. It's only 10 USD in Amazon and I put the link is below.

Tectra LIP1359 Battery Compatible with Sony Playstation 3 PS3 Dualshock 3 Wireless Controller CECHZC2E, CECHZC2U with Installation Tools https://www.amazon.com/dp/B095YF28FX/ref=cm_sw_r_cp_apan_glt_i_MAB1SES8TEBDXAABRXWT