If coming from a wedge pack, perhaps look at the Arundel Gordo or Medio bags. The gordo is a good sized back that (per the spec sheet anyway) is 1.5" wide (along it's full length). Not sure how this would compare to what you have, but also no 2nd velcro strap for the seatpost on this this design, and the material is a soft plasti-rubbery type that shouldn't chafe as much if comparing to eg. cordura.
Arundel Gordo
