That's a clean design, depending on the wall thickness, that could be pretty-strong. I think the OEM sissybar back rack has a suggested weight limit of 8-10 lbs? Not-much.
That backrest/rack is backordered, 2 months estimated restock:
https://japan.webike.net/products/21403310.html
$210 shipped, sea freight, which takes awhile. Only rated at 6.6 lbs, though, probably thinwall steel tubing.
Material: Steel Plating
Pad Size: 90mm (Length) x 200mm (Width) x 35mm (Thickness)
Carrier Size: 240mm (Length) x 250mm (Maximum Width)
Maximum Carrying Weight: 3.0kg (6.6 lbs) Not-much!
Here is what I think looks like a better one:
https://japan.webike.net/products/20535749.html
$151 including sea freight, only one item left. You snooze, you lose.
Maximum Carrying Weight: 7.5kg (16.5 lbs)
Top Plate Specification: AluminumA5052, Thickness 5mm, Black Anodized Finishing
Fitting Specification: Steel with Electrodeposition Black Painting
•It is a rear carrier using the designed aluminum top plate.
•It achieves a vehicle body form without incongruity even in a state where load is not loaded because it is a vehicle model exclusive item.
* Blinker offset will be required before mounting.
I like the looks, it's got a higher weight rating, it's aluminum, it has easy to use loops for securing a load, and the design provides for relocation of the stock turn signals.
View attachment 71495
https://japan.webike.net/products/22878734.html
HAC rack $197 shipped sea freight, estimated shipping in 1 week.
Looks very-similar to the OEM rack, but this one appears to fit a OEM low grabrail. Look closely, it may require an aftermarket grabrail by the same manufacturer. On a second-look, it appears to fasten to where the grab-bar rectangular reflector mounts.
View attachment 71496 View attachment 71497