I'm in the same situation as you, having limited easy installation options for my 2003 Liberty. You CAN buy the Mopar ones from Jparts.com, but getting them to fit is difficult. Several L.O.S.T. members here have done it, by driling new holes into the frame, grinding off parts of the skids, etc. We shouldn't have to go through this much trouble with a factory accessory.
Seems like the fit of ANY Mopar skid is hit or miss. Prime example: I installed my engine skid last night only to find that one of the attachment points on the skid doesn't have a corresponding bolt hole on my frame. See the picture. This skid is only attached by three of the four bolts, which leaves about a quarter-inch gap on the driver's side rear end of the engine skid. This is unacceptable because the plate could easily get snagged while backing up and ripped off or damaged.
I've heard similar stories from other owners. Next week I plan to return to the dealership where I purchased the skid and insist they make it fit
at no charge. I don't know if my KJ has a factory defect or the Mopar skid is wrong, but it's not my problem. They need to make sure what they sell works (and they sold me both the KJ and the skid).
FWIW, when I asked my dealership for a labor quote for installing all four Mopar skids, I was told "2-3 hours if the frame needs to be drilled to make them fit."