Aircraft to rent including insurance
 

I'll be in Iowa this summer and would like to rent a C172 but have heard that most of the time the aircraft to rent will not be insured. AOPA sell a one year insurance for $300 but this only covers $10000 of damage to the aircraft.
Does anyone know any FBO's that have full insurance coverage because I find $300 is quite steep ($100000 damage insurance would cost $1750!) considering I'll be around only for two weeks.
Or has anyone got any information on short term insurance that would cost considerably less?