Just to be sure: This is a community forum, not the company.
Fairphone employees might pop in randomly, but this is not an official channel.
As for something positive … fresh images of new translucent slim cases available now show batteries of the new batch underneath … shouldn’t be long now 
.
There were resellers with the battery in stock when Fairphone were out of stock, but now I’d suspect they ran out of stock, too.
Edit: Memolife have them in stock again …
https://www.memolife.de/ersatzakku-fuer-fairphone-2-e5326
Perhaps fairphoneangels in your vicinity could help you out until batteries are back in stock again.
Else there’s the Market .