Club 100 shows "Negative Center Coaxial DC Power Plug 5.5mm OD / 2.1mm ID"
Amazon shows "https://www.amazon.com/Generic-Volt-Barrel-Power-Cable/dp/B00304DZ7I/ref=pd_sim_147_1?_encoding=UTF8&psc=1&refRID=QTQ90Y34VEQBHYC2PGB4"; but with a positive center but long enough and cheap enough to cut and reverse.
Quick look showed several with the right connector, but wrong polarity
