Awesome tips! Thanks a lot! I'll check that out for sure - both places. I'll do it today.
And I have yet to check out rockzmom's tip. It's just a tricky thing to ask for, in Russian, in a pharmacy. If they have it, they probably don't have that exact brand. So I would have to explain what it is, in Russian.

In the meantime I actually saw something: Soy milk powder - by a Belarussian company.
It seems to be for small children and I couldn't understand the instructions for how to prepare it.. But I think that if I buy a whisk and heat the water, it will dissolve and I can then store it in the fridge.

Rice milk CAN be made from either rice flour (I couldn't see that in the supermarket - but I may not have been looking in the right place....) or real rice (although making it from rice tastes less good and is rather time consuming). Making a really "professional" batch requires some ingredients that I don't know how to get in Belarus; but it's possible to make a basic version from simply rice, water plus sugar and salt.

Either way, I had a nice latte for breakfast in my "lux" flat.
Смесь сухая безмол. Беллакт СОЯ кор.400 г /с рожд./ - первая интернет-аптека в Челябинске
Price: Something like 0.05 Euro - it's practically free!