Car was wrecked in accident but cant receive rental?

I was in an accident yesterday, not my fault, other party accepted 100% liability so their insurance company (geico) is paying for damages and car rental. The only thing is my 21 birthday is less than a month away however when i went to go pick up my rental I was unable to because they require anyone under 21 to have collision included on their policy. My personal Esurance policy is only liability. Geico was willing to provide a collision waiver however enterprise could not accept it. All the other car rental policies had similar policies SO WHAT DO I DO? The other suggestion they had was find someone old enough to put me on their policy but I dont even know anyone that could do this especially in time for tomorrow morning as the rental places will be closed until tuesday. Enterprise suggested i temporarily add collision to my policy but thats really expensive (im a college student who pays my own rent, tuition, car, phone etc) I asked geico if i was to do this through my insurance company if they or the person who hit me would cover the cost and they said no. so again WHAT DO I DO???