You might be thinking of Johnson's Rubber Roadbed. From my understanding, it is no longer made and very difficult to find. Photo here:
http://i.ebayimg.com/images/i/...6122-0-1/s-l1000.jpg
Currently, there's Flexxbed Classic by Hobby Innovations:
http://www.flexxbed.com/Page1.html
Unfortunately, you will not be able to get it from them immediately. Each order is handmade & there's a 2-week delay right now (I called them yesterday!). I hear it's a great product & will put my order in for next year.
With all this in mind, I'm going to try a very compact type of industrial felt stripping with adhesive backing (1/4" thick, combining 1" and 2.5" wide for 3.5") this year and see how it goes:
https://www.grainger.com/produ...mp;searchQuery=2FJT3
https://www.grainger.com/produ...mp;searchQuery=2FJL9
good luck!