UPDATE 28-Apr-2019: Added an Extra Long version that is 2.3cm longer. This should be more than enough to clear bigger type filament rolls.
This is my custom version of the Side Spool Mount.
This includes a Long version (as seen in the printed example), and an Extra Long version (2.3cm longer).
No additional screws needed. Just remove the back cap, slide it on to the bar, and place the cap back.
It's a strong, tight fit. So you will have to use some force to get it on.
The mount is long enough for the spools to clear the Z-axis motor.
So changing filament rolls shouldn't be an issue with this one.
It is designed for the Ender 3 Pro. Probably fits on the Ender 3 and Creality CR-10 too. But I don't have those.
Tip: If you use this awesome Filament Holder (remix) by mjoaris
(https://www.thingiverse.com/thing:3209211). Place the original mount with the flat side to the front. This way you can screw the holder on vertically, like seen in the second photo.