I made mine with a pair of the 36" paddle balloons (like these http://www.balloonsupply.com/category-s/2.htm ) and some of the water gel crystals used in potted house plants (google for "water gel crystals", also sold at Lowes and Home Depot).
I used about 4-5 tablespoons of crystals per balloon and filled with water just a bit less than the point where the balloon would start to stretch. Purge the air and tie it, before the crystals grow. The crystals will absorb the water and GROW to fill the balloon. With the 36" balloons I get a full D or small DD size.
And since the latex isn't stretched it is quite tough. I have slept in the forms several times with no leaks any damage.
They feel quite real and if you cut up an old set of nylons and cover the balloons they are quite comfortable to wear.
The only down side I have found it they can be quite "cold" when you first put them on, but after 10-15 minutes they warm up and I almost forget I'm wearing them.
I made a set approximately 5 years ago and just had to replace them a couple of months ago. They were still ok, I was just worried they were getting old and would POP at the worst possible time. My new set were made the same way.
