I finally have a scrypt implementation in pure javascript that passes all test vectors at http://www.ietf.org/id/draft-josefsson-scrypt-kdf-01.txt. I won't release it now because I plan to go for the bounty. If I somehow abandon that I will put it up on github.
Curious, have you got even the last case with N=1048576? Mine is crashing the Chrome tab it lives in, and even nodejs (message about running out of memory). (With the smaller N-values BIP38 needs it works though.)