I think I have seen those in some knife collectors book somewhere. If they ever made a switchblade version it would break your wrist.
You can get them on ebay. That's where I got mine. Like I said, that sheet metal blade guard will double the price, but you can find them without it for pretty reasonable prices. And yeah, it would put the hurt on ya if it were a switchblade! I like that it will fit in a large outside pocket of my camping backpack. I even used it to cut down some bamboo in my back yard.