No problem -- find out your shoe size in centimeters.
Lorica is better than leather because it wont stretch or shrink but it forms to your foot like leather. Getting them wet isn't really a problem.
As for sizing, there's no reason you shouldn't be able to get SIDIs that fit just right. They even come in widths! The problem may be the American sizing.
For instance, I lived in Japan for several years--just moved back to the States actually--and bought my SIDIs there. I know my shoe size in centimeters is 27. (I think in European sizing I'm a 45--don't really know 45 what!) I can literally buy shoes without trying them on and know that they fit if the size is 27 centimeters. On the other hand, when I try to get shoes in inches I'm an 8.5 or 9 and rarely do they fit just right unless I make sure to tell the salesperson that my foot is actually 27 centimeters and to look for that on the box.
One tip that might work is to look at the tongue of shoes you already have that fit right and find out if they provide a European or Japan equivilant sizing on the tag.
Motto: it pays to know your size in centimeters, especially when buying shoes that are measured in metric.