Almost impossible to make a fully compliant BS1363 plug with folding pins. But for Class II double insulated equipment you make it work as there is no need for a electrically functional earth pin. There are /were two designs, Slimplug and Thinplug. Slimplug is the better of the two and came with a C7 connector. https://plugsocketmuseum.nl/GB-foldingPlug1.html
Don’t know where to find one though.
Edit: Lindy used to do them code 48389452 but they are discontinued.
Thanks robert for that…i now have a name for a brand
and Michael i have a few devices like that but i need a mains output..none of mine seem to be able to be taken to bits to remove the power supply and replace with a mains lead