frozen wiper problems

I have a 95 F250 and a 01 F250 both have the same problem, in the winter the wipers get snow stuck under them and then it freeze's up and then the wipers don't work so good anymore. so my question is

does anyone know of a aftermarket defroster for the front window?

I have seen them on subaru cars I think that is so slick they should do that on all cars and trucks or make it an option.