by Greyryder
How wide do they need to be? You can get 1/35 scale tracks in a variety of styles at hobby shops that carry military models. AFV club sells both flexible rubber tracks, and individual link hard plastic tracks. There's another company that makes individual link tracks out of die cast metal. The individual link tracks cost more, but you can make them as long as you want.
I've got a set of AFV Club's individual link chevron style tracks on a model M60A2, and they're about 3/4" wide. The individual links are just a little bit narrower, and the side links make them just a bit over. Modern U.S. octal pattern tracks should have the same dimensions, since they see use on a lot of the same vehicles. Some of the WWII era German tanks probably had wider tracks.
The link tracks are meant to be static, but I was able to convert the ones I have to be functional. It was tedious (but not difficult), and I don't know if it would work on other styles, but the chevron and octals. They work fine on a powered model. If somebody wants to know how I did, let me know, and I'll try to explain it, here.