i bought the belkin PDA Adapter from someone on ebay and it works great:

http://catalog.belkin.com/IWCatProductPage.process?Merchant_Id=1&Section_Id= 1999&pcount=&Product_Id=91042&Section.Section_Path =%2F%2FRoot%2FUSB%2FPCProducts%2FAdapters%2F

even though they call it a PDA adapter it is just a generic USB->Serial converter

~lincomatic