You can get 4"dia by 2"wide wheels from IFI, you can also get 4" wheels from Andymark not positive about the width.
http://www.ifirobotics.com/robot-traction-wheels.shtml
But as far as blue roughtop (nitrile is the name) just search for "incline conveyor belting" on Mcmaster.com and you should see it. Select the Nitrile roughtop for the "blue" style. And i don't know if anyone makes nitrile wedgetop.
3"wide (thinnest available) nitrile roughtop part number: 5994K851
hope i helped