I've found a great place in California for treads for larger scale robots: California Industrial Rubber!
They gave me a low price quote and they have some really good stuff! They do robot treads and even did treads for a profession Wall-E robot, they've told me.
One question though with the quote they gave me: They said to guide the treads on my robot they use an "A" belt attached on the inside of the treads. The "A" belt they showed me on the inside of the treads has notches in it, which I assume go with timing pulleys. The problem is, I can't find any timing pulleys with "cogs" to pull the "A" belt.
Do these kinds of pulleys exist? Did I misunderstand the quote? The "A" belt did have notches in it, but...no timing pulleys for "A" belt to go with notches...