You might be better off making them or getting a metal shop to make them. Unless you luck out and find some on a salvage bike they're going to cost you a lot more than a little time and some steel.
Out of curiousity how are you going to support the bottoms? On the Cross bikes the saddlebags sit on perches welded onto the mufflers. You may be able to do it without the lower support but it would seriously decrease the weight capacity of the bags. All the weight of the bags and the contents will be supported by the 2 dzus screws.
You could do like they do for some of the hardbags kits and make a mount that mounts to your fender and wraps around underneath the bags.
Retired USAF, IYAAYAS!
2008 V-Star 1100 Custom Bobber project
2011 Crimson XR with Forged Highway Bars / Hard Bags / Passenger Backrest, Ness parts including Smooth Layback Plate Frame/Mount / Rad 3 Mirror / deep cut grips / drivers floorboards /shifter peg / brake peg / passenger pegs. Witchdoctor black rack, Lloydz filter / timing wheel / VFC III, 7Jurock windshield, Drag Specialties seat.