There are two pieces to the skid plate that covers the oil drain, oil filter.
For 3.5L models:
The rear skid is MR437668 List price is $103.50
The front skid is MR437661 List price is $154.95
The front bolts for it are MS240147 (4) List $1.88
The rear bolts for it are MS240180 (2) List $1.00
There are variations on color for the front skid for 3.8L models
If you provide your VIN and manufacture date I can verify if you are supposed to have different color units.
Front skid for a 3.8L in black is 5370A081 ($162.07)
Front skid for a 3.8L in silver is 5370A082 ($153.08)
You can only purchase these new from Mitsubishi dealers, either locally or online, or used elsewhere.
If you do not have a dealership near you, I'd recommend Mentor Mitsubishi online, they typically sell for around 25% below List price.
Edited by Doug C on 11/1/2009 at 6:20 PM EST