Enjoy the bike!
Shad are the obvious alternative to OEM, and it sounds like you have lost the initiative in cutting a deal on the OEM boxes from the dealer
I’m not aware of any other boxes that utilise the OEM frames, but that isn’t too serious - as lots of the systems use pretty unobtrusive/removable mounts.
Givi Outback Trekker and Dolomitis for box-shaped aluminium panniers.
SW Motech do a semi-rigid soft pannier system for the XR - not huge on capacity, but look to be pretty clever.