Simple prebuilt diverter to work with EVSE and Emonpi

Can anyone suggest a simple solar diverter (preferable prebuilt) to send unused (1.4KW) energy to an emmersion or oil filled radiator prior EV charger startup that will work alongside OpenEVSE and Emonpi

Robin Emley ( might be able to oblige with a kit, unfortunately CE rules prevent him from selling a complete unit.
I don’t know the position with the (new & updated) French version ( which is based on Robin’s design.