I recently bought a can from Walmart for $5, but I found out it works best if I do the sandwich and then let the spray dry for a day or two before actually doing the quilting.
Also I get out my duct tape and fasten the four corners down tightly to the floor. In the summer, I do wash down of the driveway and go outside to do my sandwich, gives the neighbors a reason to come over and see what you are doing!