You might consider posting a free classified wanted ad on this website, or trying one of the used parts vendors on the links page. I’d highly recommend Doug Penn.
As for your search, the Mark 6, Mark 6A, and the Wizard Super 5 all share the same lower unit. The Mark 5 may also take the same lower unit, but I can’t remember for sure. Either way, there is more than one model that used that same lower unit when you are trying to track one down.
Good luck!
JP