12 volt battery setup with an AC inverter and just use your wall wart? it is pretty low current. Or a 12v battery and something like this: https://www.amazon.com/Universal-Charger-Adapter-ThinkPad-Computers/dp/B07FY9TXNV/ref=pd_day0_hl_147_4/130-3831022-9836557?_encoding=UTF8&pd_rd_i=B07FY9TXNV&pd_rd_r=1463ca90-83c9-11e9-b428-7d17b7108ea6&pd_rd_w=GXiwL&pd_rd_wg=zQYqo&pf_rd_p=ad07871c-e646-4161-82c7-5ed0d4c85b07&pf_rd_r=458QP3J91KTX034Y3RSG&psc=1&refRID=458QP3J91KTX034Y3RSG