When I was shopping recently, this is the only pre-built threaded 126mm rear hub set I could find (not on ebay - slim pickings there as well): http://sheldonbrown.com/harris/wheels/622.html

However, when I searched the forums for Quando hubs, they received some horrible reviews. A little surprised Harris would sell a problematic hub (perhaps these are not a troubled model?). Might be worth a call - their customer service is always friendly over the phone.