Where can I buy filters (to roll cigarettes) in the center of Moscow?

Hello. You can use your own phone with the internet to achieve that information. For example, you can open Google.Maps, find the Moscow Kremlin and search for "tobacco", or "табак", in Russian, as I did it:

You can also just walk through Arbat street or go to one of malls in city center to find some tobacco shops. They will be named "Табак", "Сигареты" or sth like this.

Good luck.