I just made myself a hub pinching tool from a hockey puck, eyebolt, 2 ft. length of chain and a carabiner. For it's pinch grip companion I utilized a softball instead of a hockey puck.
The seams on the ball can definitely feel a bit nasty. Position your hand accordingly.
If you train at a more conventional gym then you might get some funny looks but maybe you'll make friends. I had a guy approach me the other night and tell me that he has been having trouble with weak hands. We had a little chat and I left him with some new avenues to explore.
I have been doing a lot of grip work so far this year. In fact I 've made grip strength into my own personal challenge as I don't have the time nor energy available to participate in a "sport" and I hardly ever get to roll in jujutsu.
Little did I know a few months back that there is a whole subculture of grip strength (including competitions) within the larger strength training milieu.
I found instructions for the hockey puck tool here.
The softball tool instructions can be found in an article by Rick Walker, Grip Strength Training for the Poor Man at the Diesel Crew site.
I just purchased Joe Hashey's new e-book Bull Strength and he includes at least 12 pages of innovative grip training methods. An awesome resource too if you want a pile of both classic and unconventional exercises to draw upon.