So far as I know, there have been a couple of people arrested for trying to do things with actual underage girls' clothing. One I think had a vending machine set-up, another on the internet. Selling things like that on the internet also isn't unique to Japan. The vast majority of Japanese society has no patience for such things.

I've been in Japan for over a decade and never seen what you're talking about (and I have been to fetish events and shops).

Framing this as an accepted thing or even a common thing or even an extant thing is disingenuous at best.