Zane, have a look at http://medfmt.8k.com/mf/postcard.html (at the moment, the site is down, but I hope it's only temporary).
Essentially, you take an old folder for discontinued film, usually larger than todays. The Kodak No.3A/2A and similar are so abundant that they are not collector-items, therefore cheap. To fit a modern 120 size film, you have to either find some old spools intended for your camera and respool the film (more difficult in the long run), or create some spacers that will allow you to use the 120film straight. There are also some other minor modifications, but nothing really hard.
Do have a look at the above site, or do a search for a postcard panoramic in the panoramic cameras section.
If you have further questions, PM me, I can take some snaps of my camera and send them to you (if I find the time, I'll add a section on that modification on my site)