Your best bet is to monitor the SBG forums classifieds section, maybe put a want to buy post there, and set up a saved search on ebay. They come up for sale every now and then, but you'll have to be patient.

If you're not married to exactly the Arbedo, the Cold Steel Competition Cutter is nearly the same blade with a different hilt, also made by Windlass. It's readily available on Amazon for $200.