every few months i buy 1 or 2 of these https://www.amazon.com/gp/product/B07R5XKD36/ref=ox_sc_saved_title_9?smid=A2KUZVNQ9LP7N9&psc=1
$18-30 ( i have 7 now ) they come back in stock pretty often, or you can get them new for $27
charge my max 85-95% very happy with them