Thank you for your feedback. We are currently in public preview of static website hosting for Azure Storage to enable this scenario. Check out the blog post here for more details: https://azure.microsoft.com/en-us/blog/azure-storage-static-web-hosting-public-preview. The feature set includes support for default documents and custom error documents for HTTP status code 404.
For any further questions, or to discuss your specific scenario, send us an email at email@example.com.David Lindblad commented
This is great idea and I really hope it'll be implemented. In addition, I believe it would be useful to be able to specify a custom 404 (and possibly a 401?!)
There are a couple factors that determine availability of Add-ons in a country.
First, Azure continues to expand which countries are supported in the Store. Currently most of Europe is supported.
Second, Store partners select which of the available countries from which they wish to allow purchases of their Add-on.
Which Add-on were you interested in purchasing?