Exploratory supports ‘Standard’ map and ‘Extension’ maps.
Here’s the Extension map store.
If you don’t find a map you want you can create your own.
First, you need to obtain a GeoJSON file for the map you need, then you can import it into Exploratory.
If you don’t have the GeoJSON file, then you can create it by converting from ‘Shape’ file. You can check the process in this blog post. (Creating GeoJSON out of Shapefile in R | by Kan Nishida | learn data science)