I've already looked into it, and have concluded it all stems from one source, Guenter Lewy, an historian who claims to have seen it somewhere. As of this date, it apparently remains lost to everyone, although the Navy was looking for it.
This gives the pro-Kerry side justification to support the "Winter Soldier Investigation" as still valid, at least from the NIS attack.
I know of no other primary source for the claim of false testimony at the WSI.
We can suspect fraud because of the shady characters, like Mark Lane and Al Hubbard, associated with it. But the WSI witnesses appear intact so far.
Perhaps the Kerry candidacy will sharpen the scholarship.