I found these online for about $6 per 100 screws. While they won't be as durable as a production studded tire or Grip Studs, they are significantly less expensive. Grip Studs are $1 per stud! The biggest disadvantages are the reduced wear resistance, and the added weight of the larger stud and the silicone.
I put 150 screws in both a Larry (front) and Endomorph (rear), and the added grip on ice is impressive. The picture of the Endo above only shows 100 studs. I ended up adding 2 more studs (inboard of the studs shown) to every other row of knobs for a total of 150 per tire. Same pattern on the Larry. 150 is more than enough for great traction, even on glare ice. I can skid to a stop on an ice rink with these suckers.
The Process: If it is dirty or dusty, clean the inside of the tire. After laying out the pattern, I poke a hole through the knob from the outside of the tire so I know where to install the stud. I used an old spoke that I sharpened. From the inside of the tire, I screw in the stud by hand using a screwdriver. I thought about using an electric screwdriver, but I wanted to have a feel for when the screw was tight. This is a tedious process, but not difficult. After all the studs are in place, I apply a dollop of silicone sealant to cover the heads of the screws (to prevent them from puncturing the tube). I give the silicone a few days to set up, then install the tube with an abundance of talc.
Here is a shot of the track left by the tires… you can even see the holes in the snow from the studs.