I have not. Just guessing but I think it might have to be custom made or uncomfortably tight. Maybe others have done this. The doctor I know that does this makes these little frozen things in a custom freezer tray meant for enemas.

Check Amazon, there are a zillion shapes and materials to explore.

Wouldn't the oil just lube it up so it would eventually get shot out like a bottle rocket?

Another challenge with this is that the formula I use has prebiotics so it's just a matter of time before gas builds up and things could get painful. I will likely just stick with my method of staying near the restroom.