Where to get spatial data for ATC airspace?
Data about ATC sectors in easy to use format, such as shapefiles, is generally not publically available. Take it from someone who has spent hundreds of hours manually importing such data from PDF text files to various GIS applications. You can find a few individual data sources here and there via Google, but they are limited geographically and more often than not, outdated.

What you need to do is locate the aeronautical information publication (AIP) of your country of interest, and navigate to the En-route section. Airspace data is usually contained in section ENR 2.1. What you will find is a more or less well formatted PDF file containing textual airspace definitions (WGS-84 based coordinates). You will need to manually transfer this text data into which ever format you need, using your preferred text editor or spreadsheet application.