I gave up waiting (got my RW in the beginning of February) and got these adapters for Yuba adjustable monkey bars.
Works great so far!
https://www.superknuckle.com/product/Monkey-Bar-Adapters-for-the-Rad-Wagon-4/31?cp=true&sa=false&sbp=false&q=false&category_id=9
Works great so far!
https://www.superknuckle.com/product/Monkey-Bar-Adapters-for-the-Rad-Wagon-4/31?cp=true&sa=false&sbp=false&q=false&category_id=9