. . . something like H&b would work without the upright bar.
That bar could be removed. If more stiffening were needed, another tube could be TIG-welded in the lateral array, but I doubt that will be case. This model fits your bike's year.
If you have the standard rack this can be added I had some aluminium plate folded, at a angle low for the front and higher for the rear. Made them out of cardboard and worked out the angles and had a metal shop cut and fold them. After I had them done I realised that I could have had them done in one piece.They bolt to the OEM rack with 6mm screws. The front plate will have to have a curve filed into it to conform with the tail piece. I had them do three sets, one for a mate and two for me. Aluminium brackets are both 160 mm wide, front bracket 30mm high by 70mm length rear 100mm high by 70 mm length. Make them out of cardboard first and check.Happy New Year regards Martin.
30 inches , 76 cm long. 12 " wide