@Doctorh3e
Are you saying that the Model-B leaked when fully inserted or that it was too difficult to fully insert? Or was it fully inserted and leaked?
There have been a number of people who indicate that they just can't get the Model-B fully inserted because of the larger diameter first retention ball. If that is the case, then you might be looking for a smaller diameter nozzle.
OTOH, if you had no problem fully inserting it, it's possible that the 1.875 inch diameter ball just seated in the wrong place to adequate seal the lower Sigmoid/upper rectum when fully inserted. I have had that occur on occasion and letting it slide back so that the egg-shaped ball seals rather than the lower retention ball, tends to take care of the leakage even though you might lose the ability to hold the nozzle in place. Most of the time it does a good job (for me) to seal. If I really want to be sealed, it actually requires a larger diameter.
I a larger diameter is called for, you might consider this:
https://www.siliconenozzles.com/SNCMED-225-Inch-Diameter-Maxi-Mediu-Silicone-Retention-Nozzle-SNCMED225.htm
I use its big-brother and there is absolutely no doubt that everything is sealed off when fully inserted. But it is not for the faint of heart:
https://www.siliconenozzles.com/SNCMAX3-3-Inch-Diameter-Maxi-Silicone-Retention-Nozzle-SNCMAX3.htm
My other larger diameter nozzle that is about the same length but smaller diameter than the SNCMAX3 is the DBLBL-3XL. The whole family DBLBL nozzles are accessible from this page:
https://www.siliconenozzles.com/DBLBL-Double-Ball-Retaining-Ball-Style-Silicone-Nozzle-DBLBL.htm?categoryId=-1
Are you asking for a nozzle that will actually make the turn and end up in the Sigmoid? You are than probably looking for a nozzle between 14 and 18 inches in length.