Car wrecked in accident, how to rent car if under 21?

They accepted full liability so their insurance (geico) agreed to pay for rental as well as damages, only there are no rental places in the area that will rent to under 21 (my 21st bday is in less than a month!) Someone else is unable to rent it for me as the charges will not be covered unless I am a registered driver on their insurance policy. Enterprise does rent to under 21 however my personal insurance policy is only liability so they would not give me the car unless I have collision. Adding it would more than double my monthly payments and geico said they would not cover the expenses if i did that. I have school/ 2 jobs/ dance etc to get to...i need a car. can anyone help me or give me suggestions? this is ridiculous, These companies dont know what to do since most drivers under 21 are still on their parents policy so collision is covered but I pay my own rent, phone, tuition, car and insurance.