/jp/ - Otaku Culture

Those if you who have air dolls or air pillows, do you use some kind of case for the insert?
Basically I'm looking for something to protect the hole and my parts from the air pressure. It squeezes way too hard if it's pumped up properly.
Looks like such a product did exist (image related), but it's no longer sold now. I looked at alternatives too, such as pet bottles, but they were either way too big or way too small.