I think I know what ones you guys are talking about. I’ve designed one that I want to be actual vinyl and look like a diaper but none of the companies I have asked seem to care.
I can see the appeal of a diaper you could control the poofiness of, but when I hear the world inflatable diaper, I think of a diaper like object made from innertube material that you inflate with a pump. Sounds fun I suppose... if a strong, plastic feel or crazy thickness is your thing, but terribly impractical.
I'll join the others in clamouring for a link, if only to see what it looks like as it's difficult thing to picture and something I didn't know even existed.