Hi Marcus,
Unfortunately there are some serious challenges with this effort.
- This part will be very difficult to reverse engineer accurately.
- The original material is a UV resistant fiberglass filled composite.
- 3D printing materials may not meet the needs of the physical and environmental loads.
- Having someone model it for you will be expensive or place some unreasonable expectation on them.
- 3D Scanning the original part might be possible but will require some experimentation and advanced skill.
I've purchased obsolete parts for bike racks before. The last resort is contacting a Thule dealer and having them order the part directly. Bigger store employees will not have any clue on how to order parts. A mom and pop shop is your best bet.
Making one yourself is a labor of love... Why buy it for $20 when you can make it for $200...
This is probably your best bet.