Custom Region Maps in Elastic Cloud Service

I'd like to add some custom region maps to my ECS Kibana instance similar to what is discussed in this post https://www.elastic.co/blog/custom-region-maps-in-kibana-6-0. I see how to edit the kibana.yml file in the "advanced" settings in ECS, but I can't figure out how to host the actual .geojson on the localhost in the cloud service. Is it possible to use ECS like the example in this blog, or would I need to build a stand-alone web server if it's not possible to host locally in ECS?

You'll probably need to host it using your own server. Are you doing things locally? You could try using something like Python's SimpleHttpServer.