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:

http://www.sfcable.com/SF-1618-06B.html?utm_medium=shoppingengine&utm_source=googlebase&cvsfa=3023&cvsfe=2&cvsfhu=53462d313631382d303642&gclid=CK-cq_GH97gCFSho7AodrHwARA