Thanks andyadcock and temmie. I found another option!
Though the titles are Birds of Europe, Russia, China, and Japan, they also cover Mongolia (as any book covering both Russia and China must). I have no idea how good these will be. But, they may be good enough. It's a two volume set of pocket guides, separated into passerines and non-passerines. I'm not expecting the best quality. But, hopefully they'll be good enough.
Thanks for the help,