One of the easiest way is to reach out to MVP's and get connections from them on who use Microsoft Stack.

http://mvp.microsoft.com/en-US/default.aspx

You can use an online service called http://builtwith.com/. This can analyze the technology stack of any company and can also provide you with meaningful reports. It has a free and a paid version - you can also search by technology and find e.g. companies in US that are using Azure.
Let me know if I can be of more help -

Building list of specific technology users can be hard, so you need a software that enriches the lead base with technology usage signals. I describe one of such examples here: https://youtu.be/2ZvVc_rCNXk