Styrofoam Beads Where To Find Extruded Polystyrene (styrofoam) Near Boulder, Colorado?

Where to find extruded polystyrene (styrofoam) near boulder, colorado? - styrofoam beads

I am looking for sheets of polystyrene foam (also known as extruded polystyrene, or blue / pink foam), which is normally used as insulation in the floor. Can be cut is cleaner than the white foam polystyrene, can be found on the packaging in a carton of the new stereo. Some fans of model building miniature land use. None of the retail stores around here carry the stuff! Where can I find in the vicinity of Boulder, Colorado?