How to buy License for Avast Pro Antivirus

I am currently Using Avast Pro Antivirus V 8.0.1506 and my subscription expires in 10 days.
Exactly how do I purchase a license file for this version.

Please note: I do NOT want a newer version nor do I want free Avast or Internet Security.
I have been using this for years, it works perfectly for me and I absolutely do not want the bloated current version.
Thanks

Contact avast > https://support.avast.com

On a note :
Using that old version is not protecting your system(s) against nowadays threads.