Rob,
That is actually not supposed to be a hard rubber piece but rather solf rubber.
Plasti-Dip makes a dip that you can brush, spray or dip and it works great and comes in several colors including black. It has a short shelf life so have everything ready to cover before opening it up. Take some old parts and practice on a little before you do it on the good ones as it takes a little work to get it right sometimes.
Rick