Late to the party, since you already returned the original rack; but here's how I would handle the problem, in case someone else wants to give it a try.

Measure the o.d. of the short brace tubing. Take that measurement to the hardware store and head to the fasteners department, where they keep all the strap steel and tubing/rods for parts fabrication. Find a steel or aluminum tube of the same diameter which you can cut and bend to the appropriate size. Seems to me that the attachment end at the stays is just stamp-pressed flat with a 6mm hole drilled in it for an M5 bolt.