If you need a new battery, I have had recent good results from Home Depot, of all places. They had fresh HL-8 (now they call it H8?) size batteries, great price, Exide brand I think?
https://www.homedepot.com/p/Exide-SP...5-49/308488577
Bring your voltmeter, check for full charge, also check the date code stamped on the side to make sure it is not stale.