I've actually figured out how to do this while waiting for the answer, you need to use the IAM CLI tools provided by amazon and then use the command
iam-servercertgetattributes -s certname
This will provide you a string like:
arn:aws:iam::123456789123:server-certificate/start_certname_com
This is the value you place in the "SSLCertificateId" value pair field
The setup instructions for the IAM command line tools (CLI) can be found at:
http://docs.aws.amazon.com/IAM/latest/CLIReference/Setup.html
Download the tool kit from aws here
http://aws.amazon.com/developertools/AWS-Identity-and-Access-Management/4143
All in all your final block will look like:
"Listeners" : [
{
"LoadBalancerPort" : "443",
"InstancePort" : "80",
"SSLCertificateId" : "arn:aws:iam::123456789123:server-certificate/start_certname_com",
"Protocol" : "HTTPS"
},...