Everyone's suggestions are great!
I planned both my Japan trips round Ayu, but my work is flexible as long as I let them know ahead of time. I'm sorry you aren't as fortunate, that sucks
If you can find Nakano Broadway in Tokyo, in that mall, there is a small shop that sells loooots of Ayu goods from concerts, TA mags, magazines, etc. I spent 200$ on just Ayu merchandise there, it was well worth the trip. Just follow the Nakano subway line (I think it's red) and get off at the VERY LAST stop. You can probably find more info about it on Google as well.
BIG BANG will be in Tokyo on December 5th, if you are into them, korean band <3