First off, get a Williams or Lyman receiver rear sight (peep sight.) Then a good fibre optic front and you're set.
In the meantime, a black magic marker over the front will work wonders.
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.