Hello my dutch friend , I'm here to help you out abit.
Although I'm unsure if you knew but the gamecards are available in various stores already.
Since I bought a physical version of the game I got 30 days of free playtime.
But back on subject, yes there allot of stores that are currently selling them:

Game Mania
Free record shop
Nedgame
Mediamarkt

If you can't find them there is always www.bol.com you can order them their with no shipping costs and if you do it before 23:00 on a workday you'll have it the next day.

I hope this will help you and let ne know if it all worked out