Surely if you have found the vehicle you can arrange the insurance on a one-off basis?
I do not know if it is difficult for a French dealer to sell a vehicle for export within the EU but I suspect there are bound to be lots of pieces of paper involved in such a transaction (there always are in France
There are very many dealers that sell Rapido vehicles and it may well be worth ringing more than one or two to ascertain about how to do it. We have used a company in Villeneuve sur Lot (20 minutes from here) now called Loisirs 47 (changed owners last year);
if you contact them (schoolboy "O" level French - failed works as I can vouch!) then we would be happy to help you in any way that we can if that proves feasible.
There may well be other companies more locally to you (I know there are some very big ones off the main road from Rennes to Nantes as we drive past them often.....), but we would be happy to help if we can..... (if the worst comes to the worst we always have a gite that you could occupy while sorting things out for a very reasonable fee
) - Bergerac airport is our local airport (flights from many of the budget airlines from the UK including Newcastle, Southampton, Bristol and Leeds as well as others.....) so we are easy to get to.
BUT obviously your first problem has to be how you could do such a thing and "persuade" a French dealer to sell you a suitable vehicle.
PS Our Swift is RHD and it works superbly at most junctions although there are a couple of oblique junctions that do require the service of my co-driver...........