iMac and alternate keyboards

[JenBMiller at aol.com]

I have recently received an iMac to use in my classroom.  I have several
alternate computer access systems that I would like to hook up to this
computer (a touch window, intellikeys, and switch interface), but the ports
for the keyboard and mouse are USB ports.  The keyboards and touch window are
different and require some kind of adapter.  Has anyone else run into this?
Is there an adapter already out there and where do I get it?  

Thanks!  
Jennifer Miller
Woodinville High School
Special Education Department Head