For those that are interested -
I had a floor liner from the rear of a 2004 Acura MDX in the garage that was left over after I sold the car. I decided to "re-purpose" it and make a floor liner to put inside the front storage compartment.
The factory liner was made to fit the inside dimensions of the rear of the MDX with all the nooks and crannies built in to fit around the wheel wells and the tie down points. I found that the front most portion was 48" wide and it was about 25" before it started flaring out behind where the wheel wells were.
I trimmed it with a utility knife to fit a 30" deep and 48" wide rectangle. When installed, the slight additional depth allowed the front edge to "roll" up slightly to a point just under the door gasket.
Overall, it fits very well. While it won't hold a gallon of water like it originally would, it will still hold a small spill or leak around the door to keep the carpet from getting saturated.
Unfortunately - I didn't have my camera with me this weekend
. I will try and get a picture later though.
Thanks to all that posted suggestions and measurements.