I used to have a tech deck(one of those mini finger skateboard things) on my desk at all times, and whenever I'd get bored or just need something to fiddle with, I'd start playing with that. I always have pens to click and spin, scissors to swing around in circles on one finger, sometimes I'll just have a pair of nunchaku sitting on my desk that I'll randomly pick up and mess with. I don't have any toys specifically for fiddling necessarily, but I fiddle with things a lot when I'm at my computer desk. sometimes I'll just randomly hold one of my airsoft guns or wooden swords, for no particular reason other than it just feels comfortable... sort of like a security blanket, or sucking one's thumb for a child. When my hands are totally empty, I feel like I don't know where to put them or what to do with them sometimes and no matter how I try to "rest" them, it just feels weird.