If you’re having trouble finding a rare jar of Fish Sauce this holiday season or maybe buckwheat flour you can either (A) find a better supermarket, or (B) visit: foodsubs.com.
Foodsubs.com gives you substitutions for loads of “special” ingredients.
Check it out.
Oh and by the way, a decent substitute for Fish Sauce is Soy Sauce – but of course you loose all the fishiness.