I mean the freehub body, the black bit on the side.
As far as I can tell there are two different types available, the STX-RC and the M290. Both are 7 speed probably compact which is a minor problem but I don't know if they're compatible.
For the casette: every 7gear casette will fit every 7gear freehub. Compact or not, doesn't matter. Als long, as your old one is not of the threaded feewheel type.