To get an MZ-1 strictly for transferring purposes, is basically useless in my opinion. Even if you find a mint one on ebay, you'll still end up paying about the same as you would for a big home deck that is more recent. Also the MZ-1 had recording time of 60 minutes on rechargeable battery that was specific to the recorder - pretty much useless in the field.
Some other MD portables that had optical out, were the Sharp MD-M11 and MD-M25, and I think Aiwa made one too. They all had longer battery lives than the MZ-1 but are probably much more rare.