I have this issue with almost every old camera I'm asked to use. I have found a helpful work around that doesn't cost the earth AND is easy to do.
the easiest way that I have found to sub in batteries for old tech is by ripping out the old cells and replacing with a modern eqivalent. The Sony beta cam power cell NP-11 outputs 9.6v at a draw of 6.2w; So, a RC battery that you can get from Amazon for 20 bucks or so would fit the bill.
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https://www.amazon.ca/Melasta-2000mAh-Battery-Connector-Gadgets/dp/B01M71H3HH/ref=sr_1_10?crid=1GKX8BP4D4TUP&keywords=Melasta+AA+9.6v+2000mAh+NiMH+Battery+Pack+with+Tamiya+Connector+for+RC+Cars+Boats+RC+Gadgets+Airsoft+Guns&qid=1679434073&sprefix=melasta+aa+9+6v+2000mah+nimh+battery+pack+with+tamiya+connector+for+rc+cars+boats+rc+gadgets+airsoft+guns%2Caps%2C328&sr=8-10
Crack open the power pack caeefully remove the old cells, solder a male jack to the battery header on the inside - drop in your new powercell connect the jacks and tape the battery enclosure closed. Pop it in the camera.
Just don't use the old charger to charge it!