The critical missing piece looks very similar to the same part on a Surly hub. What size is the bearing?..if the same size as a surly hub you should be able to use surly parts, which can be bought separately. Otherwise maybe you can replace the whole bearing, axle, and hardware kit with something thats not obsolete.

Personally, I wouldn't **** around with it too much. You could probably ebay it for $50 even with the piece missing.