You can sometimes buy it even cheaper on eBay, but here it is from a regular vendor:
http://www.oldtrailfabric.com/1000-d...on-fabric.html
http://www.oldtrailfabric.com/1000-d...on-fabric.html
Note that you need to get BOTH red and blue because your team will definitely be on both alliances at different times.
Also you might want to check out the PDF from
this bumper tutorial I made (I haven't updated it for the 2016 rules, but aside from a more generous 4-12" high bumper zone, they look very similar).