First of all, thanks for all the good suggestions. Good news is that the problem is solved. I don't know why I didn't think of this before because I was looking right at the solution all the time. It dawned on me when I was building a PVC bike lift for her bike that will raise the boom so I can close the tailgate on the truck. I took a piece of 1/2" PVC about 5" long and drilled a hole in one end and ran a #10 screw through the mounting bracket for her fenders and then mounted the sensor on the PVC. Works perfect. Just have to wait until she isn't going to ride for a day or two and paint it black. The white really sticks out. I'll post a photo tomorrow after our ride as it may help someone else in the same situation.

Update:

These photos show the method I used to mount the wireless sensor on the fender bracket. I have to paint the PVC and get a shorter screw, but it will give her a working computer until then. Sorry about the first shot being a bit blurry. It was taken with a cheap $40.00 camera that I bought to take photos of my rides. If it breaks or get lost, I'm not out a bunch of money.