Is it totally missing, or just not working. It would be much cheaper to get it rebuilt if it still has one.
If you happen to have an O'Reilly's Auto Parts in your neck of the woods, they have them, and less than anywhere I checked around here about 6 months ago for a friend. Same brand that NAPA carries, but about $30.00 less. But even at that, be setting down if you look it up. They are over $300.00..!!