hi,
The DC inp connector looks like universal type, with dimensions given.
You can buy 12V dc or 24Vdc power supplies, rated at 2amps for the 12Vdc or 1amp for the 24V version.
There are types that plug directly into a UK 13A skt, the plug assembly houses the power supply and they come with a circular connector as you describe.
NOTE: there are a range of circular connectors with slightly different dimensions, take the USA equipment to the shop when you buy.