I have those "Will hold a gallon of liquid", deep groove, rubber mats.

I just bought a back-seat set of whatever cliche brand at Sears. There are almost square rectangles. Don't know the actual dimensions maybe 1 1/2 foot long-ways.

They don't fit perfectly, but I just slid them forward to the peddles. They don't go all the way to the seat, but they cover the area my feet touch.