I was lucky enough to have an extra hole in the firewall in my Saturn,
it was right below the main one. Try and follow the wiper motor wires
or the heater wires etc.. Theres gotta be a group of wires going into
the dash, usually close to the master cylinder (where you put the brake
fluid)
I would use a straightened out coat hanger, tape the power wire to it
and poke it through. Be careful not to scrape into another wire. Have
a friend pull from the inside and a push from the outside.