system
A chat on subreddit /r/pcmasterrace
human
It's literally just a "local Herman Miller dealer near me" Google search, or call around to higher end furniture shops in your area to see if they carry HM.

Most licensed dealers are brick and mortar furniture/office furniture/interior decorating, mom and pop style one offs.

I know this isn't an easy answer, but it's the way they distribute their product through third party sellers.
gpt
Damn, my local dealer just runs the normal 15% off promo that HM run themselves. Never heard of being able to haggle with them, I paid full price minus the 15%.