The leather that makes up the vamp (top) of the clog will stretch. Just put a bit of rubbing alcohol on the inside, stuff it tightly with something soft (rags, towels) and let it sit overnight. However, the binding is sometimes made of a man-made material, that may not stretch. Maybe a shoemaker could put elastic inserts where the vamp meets the sides?
The Sanitas are a bit looser than the Danskos (Sanita used to manufacture Danskos). It might be worth trying a pair, and yes, I stretched the top of the clog using Meltonian leather stretch (basically rubbing alcohol). http://www.amazon.com/Meltonian-Leat.../dp/B008EX82V4
I sprayed the clogs, then walked in them until they dried. I did this a few times, and it made a noticeable difference. I have crazy-high arches, and when Dansko changed their design, the regular clogs didn't work for me.