They potentially go by several names, but sway bar end link is probably the most common. Could also maybe be called anti-roll bar links or something like that. You generally have to replace the whole link as I don't think anyone sells just boots for them. Should be easy enough to do though, just a nut on either end. They are like little mini tie rod ends or ball joints. Can potentially be a little tricky to pop the taper if they are really stuck, but if you are replacing them anyway you don't have to be quite as worried about beating up the threads.