Double Bass Moose amp - dead battery replacement?

[waltwallace]

I have a Moose amp that was stored in my basement unused for a couple of decades. I plugged it in to see if it would hold a charge. No green light (that I think should have lit up to indicate charging). After leaving it for many hours it works while plugged in but nothing without the power. Searched on the internets but can't find anything - probably because the amp is so old. Anyone know where to get a battery / how to replace it?

 

[en4cer]

Is that an Electrosonic amp?? I have a mouse that I just replaced the batteries in today (local battery shop had them in stock) I didn't know there was a bass version of this amp..... would like to try to find one!