They were available in POR resort store, and several stores around the park. I think they costed $65. We got ours off of ebay for $40, shipping included.
It depends on your kid, if it's worth it. My nine year old loved pal mickey, and didn't want to share him with anyone. My seven year old liked him, but was happy to let others have a turn. My four year old didn't want to carry him at all. But, that is very typical of their personalities.
My nine year old tends to find something he loves, and obsesses over it, pal mickey fit in this obsession. My seven year old is easy going, enjoys everything around him, but also doesn't have to *have* things, therefore, he was willing to share pal Mickey. My four year old prefered Donald, and didn't really care to be in charge of Mickey. If he doesn't like something, there's no changing his mind.