From what i have seen, the gray "hand" pieces are pretty common. So you can replace them by taking apart some other sets you have. Or if you have a bionicle parts bin, check that out.
That cold winter day on 2007 when my dad got me Mahri Jaller. My brothers helped me build it because i was like 4 or 5 at the time. Than i would use the crab as Jallers steed because i played a lot of MNOG at the time. And my frustration when the blaster didn't fire. Good times.
I have them in a shelf with a glass door so i could see em. They are in this order: 2001 - 2003 - Upper 2004 - 2006 - Middle (I don't have that much sets from 2004 and 2005 but i have a bunch from 2006) 2007 - 2015 + mocs - Bottom