The commercial tools are just a tube with slots and sliders, with variable friction. Almost trivial to make your own (as I did in High School), although a well machined one will be a joy to use. As such, sometimes just sliding that into the lock (WITH THE RIGHT AMOUNT OF TORQUE) will get each pin to stop when it aligns.
I had one of those tools and it ran about $70. You had to buy a separate one for each size and pin count. Could add up. It was all pretty tight size wise, machining it would be possible if you precision tools but I don't think you could make one easily with a dremel grinding wheel or anything.
I was trying to talk a friend into starting a website where you could order tubular keys cut by robot by number but he didn't seem interested. *shrug*
-- : Ethan O'Toole
