It doesn't have to be outer mongolia, I couldn't find 700C touring gear in most shops. Basically you can get anything for an MTB even in small centers, and a lot of 700c racing, but finding touring grade stuff is hard in either format. The only advantage around here for 26" is that one is probably out of luck just about anywhere for anything nice, but if it comes to a break down situation where you would put up with anythingm bet it 2.0" or 23mm, then there is much more for the former just about anywhere. So I buy what I like and carry my spares, but if I toasted a front or rear wheel on my touring bike I could get an MTB replacement in just about any house I drove by.
But the reason I ride 26" is higher performance, and that isn't going to be the same for everyone. If you tour on a 120" gear don't get 26".