I can agree at once that a set of car tires from Nokian Tires is really very rare and quite often it is out of shelf. Once , I was also looking for the most suitable tires for my car and, somehow, I've found 1010 Tires
https://www.1010tires.com/Tires/All+Season . I can say that here you will find a huge selection of tires for various cars at a really nice price. Also speaking about your model, namely R 18 W / D, I personally decided to check if this model is on. It turned out that they had it for sale.