From what I have seen, buying a motherboard is pretty close to what you already know - mostly hard to find and/or expensive. Personally, I would just buy another one because there is no guarantee the replacement motherboard will work and/or that is the ONLY problem you have.
I spilled 6 drops of Mt. Dew on a Sony keyboard (desktop) one time. The kicker is, all 6 were sitting on the keys so I would have been fine, but nooooo, my stupidity, I blew them off with my mouth and of course, all of them went into the keyboard and instantly make the keys type something different. Since then, I NEVER put liquid that has no SEALED lid near any computer stuff.