Try Auto Zone, Parts Source, and NAPA. All tree major auto parts store always have shocks and struts on for sale once a month. There most of the time buy 3 get the 4th free and depends on which shocks you buy. Some shocks are life time replacement, they cost more but worth the savings when it's time to replace them every 80,000 miles.
Good luck and hope this help, I use the Monroe Reflex on my Jimmy and find then to work great all round. Your Sonoma my be too light for the Reflex and you may find the Sensa-Trac to be more forgiving which is what i use on my wife's Montana.
http://www.monroe.com/defaultEN.asp
http://www.rockauto.com/catalog/raframecatalog.php