Adapter would have been great! Make the end a universal end so a battery can be easily put in its place.
A battery is my first option, but trying to find one that works and doesn't cost what the controller does is tuff. My first battery test will be with a power wheels battery. I have a couple on hand and always have one charged, plus theyre only $50 and you can get them at Walmart.
UDS', mUDS, COS. Weber gasser & kettle. Thermapen,Digiq2, Golden-Tiger