I just had a neat idea all you need for it is a small Lego
elastic band, an Onua claw, a Bionicle foot(diagram 1), a
Technic Axle size 2 (diagram 3), and a Technic Connector
with Axlehole (diagram 2).

All you do (Use the pics as reference) is:
1.  Stick the claw into the end of the Technic Connector
(part B on diagram 2)
2. Attach the Technic Connector to the bionicle foot (part
a of diagrams 1&2) using the size 2 technic axle (diagram 3)
3.  Stick the elastic loop between 2 fingers of the claw
4.  Loop the elastic through part b on diagram 1 and then
between the other two fingers of the claw.

And there you have it.  A bionicle foot that can grasp
stuff.  I use 2 of these so I can hang my winged Onua
upside down.