Connect to RDS instance from VPC outside region

I'm trying to add the ability to connect to my RDS instance from servers I brought up in a new region (still in an EC2 VPC). I know I can do this by bringing up a bastion server, or creating two extra boxes and running a VPN through them, but I'm wondering: is there a simpler way of doing this? Is there no way to just allow boxes in a security group in one region access to an RDS in another?