Good luck trying to find that. Freewheel hubs and unicycles are rarely sold here, and when they are, they’re snatched up within the hour. My advice to you is to just haunt the trading post every day and be the first to see any freewheel getting sold. Truthfully speaking, though, you may wait for a year or two. Alternatively, you could check out the freewheel mega thread here:
If you really want a freewheel, this thread should help you learn how to build your own freewheel hub out of an old bicycle clicker hub, if you want.
Either way, the only way you can ever obtain a freewheel hub is through a pretty extreme method.