You should be able to purchase a used one from a junk yard. They were used in 87-92 Firebirds as well is the 87/88 Fieros. If you've got a local u-pull-it yard you should be able to get one for just a few bucks.
On the Fiero they are located under the driver's side fender, just about level with the marker light. Trace the cable coming from below the windshield wiper motor, around the brake m/c, out thru a hole in the front of the engine compartment into the driver's side headlight bucket area. Part of it goes to the outside of the spaceframe thru a round hole. That connects to the headlight control module.
On the Firebirds, thay are mounted in the engine compartment, on the firewall, in the vicinity of the windshield washer motor.
They are black, about 4" square, 1" think with two connectors.