This backpack is based on Black Widow's backpack / weapon carrier in Avengers: Infinity War. The handles from eskrima sticks can optionally be plugged in to the top of this prop or you can leave the sockets empty, if you are already wielding the sticks or the staff version of the weapon.

I'm including STLs for the handle and knob from the Eskrima Stick model, which you can also find uploaded here on MyMinifactory under my account: https://www.myminifactory.com/object/3d-print-53846

I recommend using six M5 x 20 screws to assemble the pieces, but you may be able to improvise or use shorter screws. In addition to the screws, a set of connecting pieces are used to align and connect the main pieces together.
The strap system has been traditionally crafted, although I'm including a small pivot piece that takes M5 x 6 screws (one on each side).
The straps are one inch with imitation leather covers for the top strap. The plastic buckles are 1 Inch YKK Sharpn' Loc Side Release Plastic Buckles (you can find them on Amazon, for example) with a small part cut off, if you want to be 100% screen accurate.

Let me know in the comments if you need help sewing the the triangle-shaped leather part. I have included the option of attaching the straps directly to the backplate (it has 1" slots for that purpose).