Docker-in-Docker Client - Trust Addtional Root Certs

I’m running the docker-in-docker image from [here][1] and trying to figure out how to get the docker client therein to trust my private repos as they are using certificates signed from our internal PKI. Currently when I try a docker pull against one of these repos I get

Error response from daemon: Get https://myrepo.mydomain.com:9000/v2/: x509: certificate signed by unknown authority