Everything is going against you with your requirements.

Booking time is too close and at the tail end of the summer peak season; most cars in Europe are manual (therefore automatic rental cars are very expensive - usually double or more) and vans are also in high demand resulting in lack of availability and high cost. I checked Avis, Hertz, Europcar and Sixt - doesn't appear to be any auto vans available for those dates that isn't horrendously expensive (Avis, Hertz & Sixt -not available; Europcar - EUR 3,000!).

Sorry I can't be of any help.