Yes you can get a large inflatable dildo for what you need. I have one! My asshole can stretch open so widely I now can & regularly do get my ass double penetrated by two hung studs, or just ram my 2 biggest dildos in my ass. It takes a little work to get your hole wide enough to take an entire longnecked bottle or multiple dongs or cocks. A rectum will stretch a mile before tearing an inch so start getting your asshole to gape using any large phallic object & gradually increase the size until the biggest poles can enter your hole!