I don't know what the question is here? Are you looking for advice on where to buy boots? Or what type/brand to buy?
I would highly highly recommend against waiting until you're in Quito to buy boots. For one, as you mentioned they may not have your size. Heck, I've never been there and their selection might be pretty slim. Regardless, you need to break these boots in ahead of time! Buying boots a few hours before your climb will be bad.
What's wrong with
http://store.everestgear.com/index.html? I've bought stuff from their online store. They are based out of Ohio and have a couple retail stores that I know of.
Otherwise, look around on the forums for your size. If you're in the market for a pair of La Sportiva Nepals I have some for sale. Size 45. Couple years old in really good condition.