I would like to share with you a tool I created. I think it will be interesting for you if:
You want to display your data on a custom shape map
You cannot find the map you need in the required json format
I personally was confronted to this issue a few month ago: the company I was working for had a customized way of splitting their country. Of course they had no shapes for these country in any format, they just had a picture of their territories.
This is why I created ByMapSelf (in WPF). With it you can:
Draw your maps with free hand point by point or in continuous drawing
Use the borders of the shapes you have already created so that there are no ugly spaces between bricks
Add polygons to an existing shape if you need to created island, or a duplicated zoomed part in your map
Add holes to shapes if you need to add a lake, or if your shape looks like a donut
Load pictures as background to help you draw the shapes (I personally have less drawing skills than my 5 years old son)
Load backgrounds directly from the integrated web browser, and you your favorite map provider (Bing maps )
Save your work in a dedicated file format
Export your shapes as a json file for Power BI custom shape map
Export your shapes in a sql file, in case you would need them in SSRS
ByMapSelf is free for the community. I enjoyed developing it and will be very proud if it can help analysts around the world.
Please read the article I wrote on the subject. You can download the tool from here. You won't need to create an account or leave an email.