在不浪费大量带宽费用的情况下，在EC2上运行apt-get

I'm running Ubuntu on EC2 (using the alestic community AMI) and on startup my new instances use up a bunch of bandwidth running apt-get upgrade etc. Bandwidth between EC2 instances is free... anyone know if there's a mirror of the Ubuntu packages somewhere on EC2 I can use instead?I'm running Ubuntu on EC2 (using the alestic co