Once I knew the connector type for the Lepa PSU and the hot water heater socket type it was extremely easy to find cables to suit my needs and at a fair prices too! cant beat 6 feet and 12 guage for 10 bucks IMO:
I had never seen a PSU which uses C19/C20 connector. Looks like C13/C14 is only good for 10A and C19/C20 is good for 16A but otherwise they are the same.