Any of the parts stores carry them, and the price isn't too bad, $40-$60. The bad part is most are noisy, I replaced mine because it was whining loudly, and I didn't want it to quit in the middle of Winter. The replacement is louder yet.
The bottom line: if yours has quit there are reasonable pumps available, and they will probably be fine.....but loud.
Back in '85 the pump on my 79 F 150 quit, and the pump my local NAPA had was a Saginaw pump (as used on GM's) adapted to fit. I'm no expert on them, but I've read that they are a quieter pump by design. I checked NAPA and they don't seem to be doing that anymore....too bad.
1999 Ranger Extended Cab, 4x4, 4.0, automatic.