We also have a 'reversed' continental adaptor having read many posts on the reversed polarity subject.
I'm not sure whether you can actually buy such an adaptor, I had to make ours by buying a second one and physically reversing the wires in one of the plugs. I also marked the lead with coloured insulation tape so that it was obvious which lead it was...
Our reversed lead in use
We also have a plugin tester to establish the polarity in the first place.
Reversed Polarity
Corrected by the lead
I since read that a better conversion lead is made up from a short length of main (orange) cable with a reversed connection at one end. This is used at the van end of the cable run. It means that you don't need any other specially converted adaptors, continental or not.
More recently I don't bother with changing the polarity at all, this is since we stayed on an Aire in Spain which had EHU but showed as reversed. The adaptor was used and all seemed OK, except the polarity changed again on its own after a few hours and then back again a few hours later!
So I gave up and I'm still here to tell the tale