Will you register your car in France or keep it on US plates? Try contacting Marie-Emmanuelle Royer - MRoyer@patrimone.com
, tel: +33 1 42 99 60 15. She works for a company called Patrim One and insured my 964 for 5 years whilst I lived in Paris, although it was on French plates so I'm not sure if she'll be able to help if it's not (I think then you'll have to find a US company to cover you). She speaks English too!
Good luck in the move!