Sure, The mechanism works by moving the wrist up and down, so if your friends have wrist motion then the device will work.

Here are 2 links to the hardware:
2 bags of these http://www.mcmaster.com/#92735a110/=xv4dwy
4 of these http://www.mcmaster.com/#8420k11/=xv497i

you can print the adjustable rods using a 3D printer, but they are not very sturdy and they often don't thread well.

As for the sizing of the fingers (the collars) I have a bunch of sizes on file, but only uploaded the sizing of my hand, which seems to be pretty average for a man.

If you would like more details such details such as print orientation and settings let me know. as for the sizing, if you send a picture of their hand on a white sheet of paper with a 1 inch line drawn as a correlation reference, I will be able to size the hand using a computer software program.