Hi @smecher
you can order from [https://www.amazon.com/Superb-Choice-Battery-Compatible-ZenBook/dp/B07XYW818L/ref=sr_1_1?crid=3GI0KJ49C24XW&keywords=ux303u+battery&qid=1570167397&s=electronics&sprefix=UX303U+%2Celectronics%2C266&sr=1-1|Amazon] or from the [https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=UX303U+battery&_sacat=0|eBay] or [https://www.aliexpress.com/item/32830514629.html?spm=a2g0o.productlist.0.0.5dd4779b5ZUkCJ&algo_pvid=41a9c659-4831-4c31-9fd2-5db97d7eca74&algo_expid=41a9c659-4831-4c31-9fd2-5db97d7eca74-0&btsid=338d3f06-0b6f-4ed5-969a-3a2637b3b53d&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_52|alliexpres.]