The Turkish page linked above (thanks for that, NON) looks like it would work.
In the grey field the email address (E-Posta) should be entered, and re-typed in the box below.
Next, in "Ad-Soyad" goes your name.
Set the country (language).
The three letter code should be typed, and the box below should be ticked if you are using Avast at home in a non commercial environment.
Another possibility may be to try the secure registration. Move down the page a little, and click on the link in orange writing, in English,
"try register here
" which leads here.
I don't know if this secure page will allow a key suitable for 4.8 to be produced. Worth a shot, though.