egr
If you have a fry's anywhere near you they will have them. Radio Shqack should have them but as you have already found out they do not pay attention to theier stock on items like this. I wounder sometimes if they just wheel in a new cabinet every 6 months or so.
I spent maybe $3 at fry getting all the resistors I needed for the egr eliminator along with all the other three or four sensors and stilol have a pile left over.
There are thousands of places on the internet that sell this stuff cheap. You can buy a pack of ten for like $1.50.