Inner positive? Inner negative? AC on the connector? 3-pin to allow I2C/OneWire data-transmission to the PSU? Deep or shallow? Straight or right-angle? It gets kinda crazy after a while, even if you can find a combination that *physically* mates.
Maplin do a nice kit of polarity-reversable adapters and cable - I found this would handle something like 75% of things like non-smart-charge laptops, set-top-boxes, routers, scanners, WiFi modems, portable-radios... I even learned to superglue the reversible-bit of the plug together once the right orientation was determined, after someone yanked the cable, the reversible-bit came apart, and they replugged it the wrong way round.
https://www.maplin.co.uk/p/dc-output...tion-box-n98ap
https://www.maplin.co.uk/p/3a-dc-out...able-18m-aq81c