There is a Russian shop in Rheinfelden (Germany) www.city-markt.de
, which is very close to Basel. I know the Russians from Basel go there, but I have never been.
The shop I go to is also in Germany, in Waldshut-Tingen, which is about 20mins drive from Baden www.mix-markt.de
I could recommend the products by Monolith under the brand of "Погребок" (a cellar). If you need the address, I can look it up - could not find it on their website.
You should be able to get smetana in those shops as well.