His insurance company should cover a rental car for you ASAP. If you need a car today, rent a car and start sending them the bill.
(this assumes that you don't have rental car coverage on your own insurance already, which would be even easier)
EDIT: @&*#(@*&(# you Kelly, I knew I should have hit post after the 1st sentence, that second sentence cost me!
Anyway, ditto.
)