Supposedly Jens (Individual Computing) is going to be releasing a Zorro-based networking card soon. Several people have been dumping their old Amiga networking cards on ebay based on that speculation lately, trying to make some $$ before the release of the new board renders the old cards completely obsolete. So based on all that speculation you could look for an old card being sold, or wait for a new card to be released.
Alternatively there are ways to use a serial link, am sure someone with instructions will come along soon. Good luck!
