Hi! Unfortunately, I have a different interface as the developer, so I can't see exactly what you're seeing.
The button you're looking for should be called "External keys" - it should appear somewhere in the download section of your purchase page.
This might also be related to your user account settings - check if there are any preferences that could be hiding external key options.
Since I've confirmed that Steam keys are still available for both games.
Let me know if the "External keys" button still doesn't appear!