Are there non-latex balloons made?

There has been a lot of interest lately in finding alternatives to natural latex rubber.  To this date, there are no alternative in production that gives us the properties needed for our balloons.  This question is usually asked by people that are concerned about latex allergies.  The properties of latex rubber balloons, specifically from the Hevea brasiliensis plant, that make them appealing for balloons have NOT yet been reproduced in other materials, or at least not in any commercially available product.