I had never thought to use a Chicago screw. You could substitute a piece of metal tubing if you didn't want to use rubber tube. I know you can get Chicago screws from MidwayUSA, but I'm not sure if they'd be long enough to accomplish much. McMaster-Carr has a larger selection.
If you prefer a tab, like the Krebs enhanced safety, you can buy just the tab from Solar Tactical. If you are going to try and attach it with a couple small Chicago screws, you could use washers for spacers, but it's probably best to use rivets.