Online you can buy it from Pfeil and Holing (http://www.cakedeco.com); or Albert Uster Imports (http://www.auiswiss.com); if you are near a Trader Joe’s or Whole Foods, you might ask at their bakery dept because a lot of mousse cakes will use the strip to keep them intact; they might be willing to sell you some.
You might also try Country Kitchens but I don’t know their website off the top of my head. They’re in the mid-west I think.
In fact, I wonder if KopyKake has it - at least they’re closer to you. You are looking for “clear cake band” if you decide to google it.