Have lots of lightly used feeder batteries. 12v 7ah and 5ah. $5 each. Guaranteed to work and hold a charge. Most are about 1 year old. And stayed fully charged in ups systems. Sold some on here in years past and guys have been satisfied with them.
If you get one that doesn't work for some reason I'll gladly replace it. Free to test when you pick up. Located a little east of Gainesville Tx