All those commercial change tents (they aren't tubes...other than the Sunbounce) are good products but there is one major problem with them...portability. Oh sure they are light and pack down well enough but what if you are doing multiple costume changes in multiple locations? Do you really want to pop them up, take them down only to have to do this numerous times? A tube is far better, however the one from Sunbounce is too small/short. You might as well use a towel.
A fitness/swimwear photog I know has his own setup...basically 2 big (key word: big...as in at least 36" dia.) Hula Hoops and some material (bedsheets) pinned together and over the hoops. He's well over 6', so when he lifts the top hoop the tube will work even for Amazons! Cheap, effective. The only bad thing about this is that the tubes don't break down, but you can gather it all up together and sling it over a shoulder. Of course you need room in the car to carry these hoops.
Another reason for a tube?...wind. Have you ever had to chase down a tent that the wind caught? Same thing for these popup changing chambers. A tube lays close to the ground, ergo...no wind concerns.
I'm looking to make a breakdown version myself using small PVC piping and 45 degree elbows. It won't be round like a hoop (more so it'll be an octagon) but I should be able to figure a way to make it extremely portable.