the hardest things to find are particular kinds of veggies and spices that aren't common on this side of the globe. The supermarkets in the region are also fairly small, so they usually don't have a section with these kinds of lesser known ingredients. And there aren't that many special shops that I know of that sell such ingredients. Heck, I'd have to make a big tour just to get my hands on kvass if I ever needed it.
Most baked stuff I could make, since dough mixes use pretty much the same ingredients everywhere, but outside of that field I might have issues.