I haven't made them myself, but I have sewn with mexican oilcloth which is similar to the PVC plastic. One thing to remember is that the plastic can stick to the foot of the machine and you can get uneven stitches. I read somewhere that if you use tissue paper or greaseproof paper it can help with that.

They would be pretty easy to make - make bags all the time that are so easy so all you would need to do would be cut the plastic the same size as the fabric and sew as a double layer kwim? If you like I can email you my bag pattern that I made?