Regarding bear crawls, here's a possible variant: remember "wheelbarrow" races where someone holds your feet and you "run" along the ground on your hands? You can get a partner and take turns being the wheelbarrow for some specified distance or time.
Another grip exercise for those in a gym without a fat bar: load up one end of an oly bar and grab it by the thick end (between the plates and the end of the bar). Hold for time with the other end on the ground or in a rack, then switch hands. Pretty simple, but effective.