Bump Dots can be used to make all kind of knobs, buttons, dials, etc. accessible. One never knows which ones will come in handy when. I like the "Entire Set" assortment pack, Item Number: 1146-13 way down there at the bottom of their page. $34.95 for 434 tactile dots of all kinds of shape and sizes. Money well spent.
In a pinch, todo: WalMart dots, rings and tape.
Sorry. See the other labeler listing.