[br]
I solved same by getting a 4 aa battery case and connecting to the ac power port.
Parts available on ebay but adapter kit needs to ship from china. I got lucky and found the right plug in my wall wart collection.
https://www.ebay.com/itm/For-6V-4-AA-Battery-Pack-Holder-Box-Case-ON-OFF-Switch-with-DC-2-1-Power-Plug/254382505090?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
https://www.ebay.com/itm/8-Tips-Universal-Charger-Power-Supply-Adapter-Plug-Jack-Kit-for-Laptop-Notebook/114564782817?