New materials come and go. Today, we have fun fake furs and lots of acrylics and blends. Back when I was a little girl, we used a lot of angora and wool. Some brands are no longer available.
However, we are blessed. If you are reading this, you have access to the Internet. A web search will bring you some substitution sites. Try to narrow down your search, though, by using more than "yarn substitution" in your search. Add the brand name and the weight, if possible.
Here are two sites I found in a very fast search. The second one requires that you register, but it's free, and I hope to check out their database of vintage yarns ASAP. When I do, I'll give you some feedback. I know my old Workbasket patterns will put it to the test.
Some substitutions are easy because the gauge is given and a clue, like "worsted." Not all are that easy. One site suggested just searching for the yarn and see what pops up in the search engines.
Either way, I am really having fun going through these old magazines.