You need to get your insurance company to hire an attorney for you at its cost or you need to contact the city attorney who handles this police department and explain what needs to happen. You explain that you have an estimate for labor but a part like this is rare and you need to find out whether you need special repair on the existing bumper or if your mechanic has to pay top dollar to pay for a bumper since it is not an out of box product (i.e., it is a classic car).