Questions about a 512k

Hello everyone,

I just bought a Macintosh 512K for $5.
The seller knew what it was and what some sell for, so I don't feel guilty.
It's too late tonight to see if it works, so I can post more later.
It's in great physical condition. It has a keyboard, but no mouse.

He said it worked the last time he used it, but that was years ago. Even if it is dead, I'll keep it as a decoration.

Two Questions:
1) Where is the best place to look for a mouse for it?
2) The battery in the back is corroded. Where can I find a replacement?

Thanks everyone!