The Original Ducati Top Box is made by GIvi, and the lock system is the Monokey. So, you can buy the orignal rack parts as "spare parts" in any Ducati seller. The list of parts below, and for the mounting manual search "Top Case Assembly Instructions 96780582A". In my opinion Original looks very much better than Motech. The price is very similar. I buy these, and use my Givi Maxia E52 without problems.
Desc. Ducati Ref. Qty.
RH Strut Support 473.1.D13.1AA 1
LH Strut Support 73.1.D14.1AA 1
Spacers d7xD10xD15 H19 713.1.B27.1AA 4
Clamp Plate 829.1.E23.1A 1
Rubber Pad Rear Plate 822.214.171.124A 1
Rubber Pad Front Plate 8126.96.36.199A 1
Rubber Pad Clamp 8188.8.131.52A 1
Support Plate Top Case 829.1.E22.2A 1
Screws TBEI M6x15 c.10x6 7184.108.40.206A 2
Screws TBTI M6x30 718.5.039.3CA 4
Flanged Nuts DAX M6 749.4.031.1A 2
Screws TBTI M6x25 718.5.037.3CA 4
Screws TBTI M6x14 718.5.032.3CA 2