I got some Bell bags at Wal-mart. $10 each. They're not very deep but sufficient for my needs. They're made to attach to the handle bars with velcro straps, but they mount nicely on either side of my luggage rack.
I'd like to find some deeper ones. perhaps fabric coolers or small backpacks would work with a little ingenuity. Follow the yellow brick road to WallyWorld and let your imagination soar.
I've been doing SaddleBags for quite some time now. Here is my bike and a link to my webmasters bike. Here is Dale's bike. http://www.simpsonmotorbikes.com/DALEBAGStn.html
I just sold 3 sets, and do not know what I have left in stock, but I can surely order more.
JUST GOT A SET OF THESE. THE SIZE IS GREAT FOR A WHIZZER AND THE PRICE IS NOT BAD. ALSO GREAT QUALITY. YOU CAN PICK THEM UP HIGHER ON THE BACK RACK SO AS TO KEEP OFF OF THE MUFFLER.
eBay Motors: Leather Motorcycle Saddlebags Tool Saddle Bag Small 360 (item 200233319082 end time Jun-25-08 17:32:52 PDT)
I'm thinking of making some hard bags out of marine plywood, using the stich and glue method from kayak building. You just wire 3mm plywood together with copper wire, and fill the edge with epoxy. Then remove the wires and fill the corners and paint it with thin clear epoxy resin, adding fiberglass cloth if necessary. Waterproof seals can be made with foam and nylon hardware.