RHEL subscription manager issue when creating RHEL container images using AWS Image Builder

I'm trying to use Image Builder to create RHEL containers. Recently, Red Hat made changes that essentially force your image build to run on a RHEL host. Rather than just running subscription manager (which used to work on non-RHEL hosts, but now results in "subscription-manager is disabled when running inside a container. Please refer to your host system for subscription management."), the Dockerfile needs to copy some Red Hat specific entitlement files from the host to the container in order to use the RHEL yum repositories. Red Hat documentation on this new approach is here: https://docs.openshift.com/container-platform/4.7/cicd/builds/running-entitled-builds.html

Note that I am currently using CDK to configure my Image Builder infrastructure. It seems that about the only option available is image type (e.g., t3-medium) - there is no option to specify a different OS or a specific AMI to use for the EC2 instance that will run the docker build. If there's a non-CDK approach (such as using the aws CLI) to create a RHEL infrastructure configuration I would be open to it, but would prefer a pure CDK solution if possible.

I realize I could launch a RHEL EC2 instance with docker installed, etc., and essentially roll my own solution for doing these docker builds, but I'm already using Image Builder for other container builds, so I'd prefer to find a solution to this problem that doesn't require abandoning using Image Builder just for the RHEL use case.