Etech Caravan Supply Leads, 16 amp, IP44 or IP67 weatherproof ratings, extra heavy duty rubber 3 core 2.5mm flexible cable (to AS/NZS3191). These leads use Gewiss caravan type IEC309 3 round pin 16 amp connectors on each end. 

Buy direct from the manufacturer with a 10 year warranty, every lead individually tested to AS/NZS3820:2009 A1. Why pay more for rubber flex? Rubber flex has superior flexibility and temperature characteristics to PVC so will outlast a PVC lead.

CL16-20-IP44 - 20 metre lead, IP44 weatherproof rating
CL16-25-IP44 - 25 metre lead, IP44 weatherproof rating
CL16-20-IP67 - 20 metre lead, IP67 weatherproof rating
CL16-25-IP67 - 25 metre lead, IP67 weatherproof rating