Ok so after some tests, I was able to just create an additional docker registry as a private registry. Then I would pull the elasticsearch image from elastic.co, add a tag and push that image to my private registry. Then I would add another entry to my registry-mirrors setting for my daemon and include both URLs for my proxy cache and private registry. The reason why they are separated from each other is because you cannot push local images to a proxy cache registry.
The reason why I'm doing this is because our users don't have direct access to the internet so they can only pull images from docker hub because of the proxy cache, now they can pull images from other registries as well although there is a need to pull and push images regularly.
I am also looking at Nexus 3 Repository Manager.