Hi @suzanneoi ,
Here’s the ifixit [guide|29844] guide, that shows how to replace the battery.
Replacement batteries are available online. Just search for ''CS-ABD003XL Battery'' to get results for [https://www.amazon.com/Replacement-Battery-170-1032-00-170-1032-01-GP-S10-346392-0100/dp/B07NK8LQXV|suppliers]. Supplier shown is only an example to give an idea of the cost the battery. There are other suppliers online that may suit you better