I use the Bald Eagle with the carrying base. I got it through Grizzly Machine as they had the best price in the country at the time but I believe they only have front bags now.
SEB Standard Rear bag is $105 shipped or the Bigfoot $145 shipped (both with 3M Ears) is available with spacings between the ears: 3/8", 1/2", 5/8", 3/4", on up to 3" wide.