On my sample size of 2, all of these brackets have been broken or missing due to the screws failing after multiple (many) collapses of the stroller. Wasn't able to find it on Babyjoggers overpriced spare parts site, so drew it instead. Replaced the broken screws with 4mm tapped rod, added 2 discs and bolts, and grinded it down with an angle grinder.
Flip in your slicer if you need the other chirality.
The author marked this model as their own original creation.