I had to find the damn chuck key first, to change the drill bit out, to let me drill the hole in the chuck key, so I could attach the chuck key to the lanyard holder, so I wouldn't lose the chuck key again... All in, it was a 20 minute search for a 30 second operation but that says more about me than it does about the project...
My dad used old inner tubes for a lot of things, including a holder for his drill chucks. He would attach them to the end of the power cords.
On portable stuff I do the same. For grinders, I use zip-ties.