firefighter -
A bit more information for you. You'll need 6mm (diameter) X 1.0mm (thread pitch) bolts that should to be 20 - 25 mm long. I forget which length, but I think either will work.
If you read (search) this and the Problems/Annoyances forum it will be clear that the orignal fastners are of very low quality. Many have broken or the threads have stripped. I'm sure we cannot blame everyone that has had a problem because they over tightened the things.
So when you re-install the skid plate don't over do it. With high quality bolts you may strip the threads of the captive nuts - but the bolts will be fine.

dave and xtoy - you've been warned