Bob,
I've been able to purchase a replacement unit on EBAY for at or below $50 in the past.
Also, check the online junkyard inventory at
https://www.car-part.com
Make sure you get your part# off of your unit first, as many of these units look identical. Also, the part# on your vehicle will be different depending on whether you have a replaceable filter or not. ... unfortunately, I'm not sure exactly what that means.
Phil at Fastlane also sells them, although the part is pretty expensive. There is also a superceeded part number out there for your unit, so I think there are actually 2 part #'s that will work.