Many of the knives in this story—like the Swiss Champ and the Leatherman Wave—are available in stores. Others, such as the D.E. Henry Bowie and the George Herron Model 6, are either out of production or custom-made. And you'll have to wait for yours or do some work to get one. There are older Randalls out there that you can see at Knifemakers Guild shows, or buy on eBay.
For the really scarce stuff—knives that came out of one-man shops—you are going to have to dig. The way to get one is to call as many custom-knife dealers as you can find on the Internet, tell them what you want, and see if they can find it. They can often pry a knife loose if the price is right. And that price will be fierce.