I have a nifty little rack for my roadie; a 'Bontrager Backrack Lightweight' that mounts using the rear skewer.

I realize that this is an "Interchange" type rack that can mount Trek/Bontrager's line of easy off & on racks.

However, I want to get a non-dedicated trunk bag (with standard mounting straps) that I can also use on other racks/bikes.

This rack's width is relatively narrow, about 3.25" at the tail end, 4" at the front so, it's not perfectly rectangular.
--The Ortlieb Trunk (with the smart adjustable gizmos underneath) does not fit due to the non-rectangularity of the rack.

Any suggestions for a sleek (non-shoebox) designed bag would be greatly appreciated