I thought I had lost the file, but thankfully Ian Hubert managed to find his copy. He used the balloon/blimp in the motion picture Ideality, which is free to download. So I added the file to the page where you can already find an image of it in my 3D graphics section. Big thanks to Ian, because now we can all play around with it. Go see Ideality, and the new movie Ian is working on (and I get to help a little with) Project London!