Ok, yeah that's closer. So like, on beachballs, balloons and the like, I can give this information.
Beachballs like that, not only is 5 foot... kinda big. I'm kind of looking to see if I can pull off "pretty dang big" without being like, cartoonishly crazy. (though honestly might be fun if somehow plausible to like get to the "oh no I'm immobile!" bit of it somehow and still be able to have sex.) but more importantly Beachballs tend to be made out of the jaaaankiest materials. They're rough, and let me tell you, one lil slip of a sharp edge on those seams and the fun is over.
Now, an inflatable bra would be kind of a cool idea. I had an idea for a bit, though honestly might be a stupid one, but like, if there were some kind of pumpable bra that had like, a little pad for inflating it, with a tube. Then that could be placed on a crotchless panty set just above the downstairs kind of area. Then, literally with each thrust, it would expand the chest! Very regrettably, I seem to be one of very few people in the world interested in such a device and haven't found any seller making something like that.
What I was kind of initially hoping for would be something like what I just described, and was wondering if perhaps some other lady on this site would see this and be like "Ah here, go to
www.thissiteyouneverheadof.com (not a real site, I don't think) and you'll find exactly what you're looking for!"
But alas, my search doth continue.