USB powered "fake" battery pack adapter?

[Zaphod]

I don’t think any system that would normally take 4 AA or AAA batteries would mind 5volts instead .... you’re only talking ~200mV difference.

You could stick a USB socket on the product and wire the outer two connections directly to the original battery terminals (obviously you’d have to block simultaneous fitment of normal batteries somehow)

Here’s some example sockets you could use https://www.ebay.co.uk/sch/i.html?_from=...t&_sacat=0