have you thought about using the cheapo mass produced fake hands there quite good , but i usually buy mine from china dirt cheap but i think you too late for that , if not try Ebay .
you can fit wire into these and make more adapted hand postures , i hope this helps .
I use various zombie hand yard stakes like the ones in the link below. I insert pieces of 1/2 inch flexible copper tubing into the fingers and bend them to the position I want which includes holding things. After bending the fingers into the position you want, you can also hit the fingers lightly with a heat gun so that the plastic fits their new shape better. I did not hot the hands in the picture below with a heat gun, but probably will this year.