Nik Collection 2018

I already have just purchased PhotoLab 3 and Viewpoint 3. I plan to purchase Nik Collection 2, but not right now.

I downloaded and installed Nik Collection 2018 on my MacBook. The problem is, that while I was able to get the trial version (good for 30 days), there was no way to buy it - as I read elsewhere, the cost was/is $69.

How do I get an activation key for Nik Collection 2018 ?