Chris,
Unfortunately, nobody makes them any more. Rotman plastics in Worcester, MA was the only company that ever did make them to my knowledge - they went out of business a long time ago. I guess after the 1975 Topps mini set came out, there wasn't a need for them. I luckily found a dealer at a Boston area show about ten years ago that was selling the last he had of them to get rid of them and bought all he had. Sorry, but I don't have a single one left and I think the only way to get any now would be to special order them through a plastic packaging company. Sorry I can't help you more.