Amigakit sells the PCMCIA wireless card and also a program called "EasyNet." It is a graphical (kinda) front-end for AmiTCP 3.0b and acts like Miami; keep in mind that while Miami & MiamiDX support LPR printer devices (allowing printing over your network) AmiTCP does not. There is a "sticky" discussion about using wireless cards and Miami on the AmiOracle Forum of AmiBay.
You can obtain a full working copy (2 disk) of AmiTCP 4.23 from the web, but don't expect it to work. A "key file" for MiamiDX is out there too, and gives full functionality. Same for IBrowse2.4 and Voyager 3.22.