I love java moss but it is so expensive I could buy a betta for the cost of the moss and I know which I would rather have....thought....work at school....and I reckon I spotted some java moss in a tank in another classroom... I must investigate this further next week...
I get moss from a couple different LFSs and it's usualy anywhere from $1-5 for a huge huge clump of it. I love the stuff, I have it in every single tank, it serves as a nice cushy bed for them
I found some at Petland of all places... just takes some looking around. Ebay and aquabid both have sellers. The stuff grows pretty quickly if it has alot of light. My girlies like to lie about in it like the princesses they are..... 8)
I get my Java moss for free.... I called the LFS and they said they didn't have any sell-able clumps, but I could come by and they'd see if that had any little pieces I could have... so I came by and the store guy managed to pull a sort of -palm of your hand- amount out of all the fish tanks they had there, ie: bits and pieces from each one, and he didn't charge me saying he wasn't sure if any of the peices had roots so he couldn't promise it would grow.