I know you ask for local sellers. But if you are patient, you can get Smallrig. I got mine for my Z6 with 10% discount using code shareasale10%. I think Riceball sells too but more costly.
SmallRig L-Bracket for Nikon D850 2232 is custom designed and formfitting, with a anti-twist safety pin on the bottom to prevent the camera from twisting.
Will strongly recommend getting a RRS L Bracket if you are looking for a good one. Its expensive agreed but definitely good quality, finish and fit on the D850.