I was hoping there would be a way to find a fossil and turn it back into a Sheildon...
You need to go to twist mountain and there is a man that will give you a random fossil daily (excluding gen 5 fossils).
Here is a video of how to find the man: http://www.youtube.com/watch?v=egpRb95vUoA
If he does not give you the armor fossil the first time, just soft reset until he does.
After doing this just go to the nacrene city museum and restore the fossil.
You can get it on white 2 on this way
http://bulbapedia.bulbagarden.net/wiki/Yancy read this she will trade you a shieldon.
http://www.youtube.com/watch?v=6tynRywgmn8 Watch this
Hope I helped ////jofly