1) Sarah found a hire car company who's policy on roof racks seemed to be 'do what you like, just don't damage the car' - see if she has the details.
2) The club has a set of inflatable roof racks, but i recall they have a hole. If ya could patch them they might be good to go.
3) anne found that streetcar allows roofracks as long as they are proper ones that go with the car. streetcar works out to be quite pricey with a per hour charge and a milage cost also, but its an option.