When my parents were together, my father was totally afraid of balloon-type retention nozzles.
On two occasions that he will still admit to, he reluctantly used one on Mom at her insistence and direction.
Mom realized that all of Dad's enema bags were the “Faultless” brand, same as one of her several douche bulbs.
That one happened to be the pink one. At the time all “Faultless” brand used the same thread, so a hose stopper from a “Faultless” brand HWB-type bag would work, and make a tight leakless seal with that pink bulb.
So, she devised a retention tool which works as follows. Once the bag was inside him, she would first make sure the valve was closed. take the pancaked bag down, unscrew that stopper, and with the nozzle still in him and the stopper closed screw it into the pink douche bulb, and set it aside, often by his right knee, and allow him to go through his normal retention sequence. If he was short of the 15 minute retention time (most often on the second enema in a session) She o8uld then hold the bulb higher than his rectum, open the valve and turn the bulb stopper down squeeze gently, then lower it below his rectum stoper up, and let it re-inflate. She would keep doing that until he could hold it by more conventional methods.
This DID become an effective retention tool, and he was encouraged to use it on her.