All-Pro would be the premier supplier for SAS, they pretty much developed the SAS as you see it today, plus they are right down the road from you in Hemet. Other than junk yards and such I wouldn't know where you could find one, you may want to see if All-Pro has someone they deal with. Sorry, don't know of anyone there. Maybe if you hook up with one of the local clubs you could get some direction. Two major groups come to mind in the SD area, Tierra Del Sol Four Wheel Drive and San Diego Four Wheelers would be another, here's their websites:
http://www.tds4x4.com/http://www.sd4wheel.com/Now as to not wheeling an IFS my question would be why not. I personally have had several and have wheeled them as hard as a straight axle truck and have never had any problems. The Toyota IFS is not to be taken lightly it will do the job, sure it is not able to travel as much but with the right set up it does just fine.