3D printing pricing has dropped dramatically, you could buy your own 3D printer kit for around $1500 for a decent one and make them for pennies on the dollar.
If you needed faster production an injection mold would be the way to go. For something simple like that you would have a single mold base with a few different inserts for varying sizes. Mold would cost approx $6000 if there's nothing complicated. Price per molded part would be approx 25-40 cents depending on type of plastic.
They could be made out of a hard type rubber, that had an undercut that allowed it to flex and snap over various turret Sizes. And with rubber being used if it snapped down to below the rotating portion it would lock against the main tube and the smaller diameter of the turret.