Oh my … I suck at hand drawing
Here is the idea I got :
A can rotate around the X axis, it can be stopped with the “a” screws.
B can translate along A as long as H1<z<H2 + B can rotate around A (Z axis in this case), automatically stopped by friction.
C can rotate in any direction as long as the angle it is making with B is less than something like π/6 rad
The stem can rotate around the Z axis, if needed to.
Not as flexible as the one in the video, but easy enough to animate (at least I hope so).
I may change the length of A and B.