The under slung caliper mount is lighter and easier ( physically smaller ) to fit up , anytime you are messing with the rear wheel , for me anyway . The caliper is compatible with the stock ratio pump , you will be up for a bracket plus the caliper and a new line , depending on how long that blue line in your pics is . The caliper comes with good pads , so no worries there .
ACTIVE : Rear Caliper Support (Brembo 2P&Standard Rotor Diameter) [1470093B]
Product Description: KOHKEN (KOHKEN DENKA) Rear Caliper Support [Color Anodized] [KOK-1313-OR] : Fits:SUZUKI GSX1300R HAYABUSA 08-12:brembo 2 pot caliper for ... - Webike
japan.webike.net
Product Description: AGRAS Rear Caliper Support [317-391-000] : Fits:SUZUKI B-KING : SUZUKI GSX1300R GSX1300R HAYABUSA(GSX1300R HAYABUS... - Webike
japan.webike.net
There is 3 options , the middle is offering anodized colors other than black and silver natural . All are a bit pricey , but Agras the worst price .
The Active will be most likely best option / value , and available .