[Clic Clac]

I think there is also a Crit'Air sticker site for "international" folks - and it is (or was when I found it) in English.

The above site also offers English & German.
And it carries a warning about scams surrounding the sales of the stickers.

As I mentioned above DON'T USE THE PHONE to purchase one.

 

[Clic Clac]

Another point to bear in mind - for anyone with an 'old banger' (Groups 4&5 I think) - is that cities not yet in a Crit'Air zone can sometimes ban these vehicles during periods of high air pollution.