Newel Post Suppliers??

I have a client who is looking for a new staircase system & they are requesting Hard Maple newel posts. They want a post width of 5” or 6”, plain straight posts, no bevels or any groove cuts needed.

Does anyone have a reputable supplier who can deliver 5” or 5” posts? I’m having trouble finding anything over 4” wide.

Alternatively, a 6x6 through the planer?