Well see that`s the part where the velcro comes in. Universal is the main reason for it. Two small slits cut towards the top of the tube and two small slits towards the bottom with velcro strip ran into and through them so you then can strap the velcro around a Chuck or whatever other device you have. Or I`m liking the strong magnets idea myself the more I think of it.
The velcro would work for sure but the magnets need a good testing run on that idea.
See that attachment in these pictures was actually one of the two things that in fact wasn`t really there in my picture but done in Paint feature. And the bottle wasn`t cut out of the tube area yet for squeezing it.
I am going to turn my Tundra mod into the real deal today or very soon. All I need is to snag a brass fitting for the cart off my sister.

And some velcro stuff. But I do have the powerful magnets already for giving that a try.