I updated my profile. I had forgotten I never finished filling it out.
I bought a generic shield from Tractor Supply. I cut it to fit, using the salesperson's suggestion of cutting equal lengths from both pieces. I still had vibration problems. What irks me is the original JD shield only failed at the upper tube. Not knowing that pretty much every section of the shield could be purchased independently, I threw the whole thing away. So instead of just spending $26, I need to spend $136 for a new JD shield. If you live long enough, you may actually learn something.