So I was about to get a shower and had turned on the water, when I decided to move the shower head (one of those removable massage heads) towards the wall as to not get the bathroom wet. Well, the plastic threaded cap had been slowly cracking and decided at that moment to fail, sending the shower head to the floor of the tub and spraying water everywhere.
After no small amount of cursing and heading out to buy a replacement adapter, I noticed something when picking up the plumbing fragments from all corners of the bathroom:
One perfectly sized o-ring, ready to be pressed into service on my Mudman. It works great.