Amazon.com: AAOTOKK (2 Pack) USB to DC 2.5 × 0.7mm Power Adapter USB 2.0 A Male to DC 2.5×0.7mm Male 5 Volt DC Power Charge Barrel Connector for Tablet,Access Control Attendance,Electronic Dog.(M/2.5x0.7) :
USB to 5.5mm*2.1/2.5*0.7/3.0*1.0/4.0*1.7/3.5*1.35 Barrel Jack Power Cable 5V DC | eBay