Brattons sells the 3 hole front seat brackets, you can cut them down for the passenger side. They also sell the front seat hinge piece, but dont' apparently sell the long "carriage bolt" to go with them. Of course the windshield swing arm nut is used on the inside of the bolt, which Bratton's also carries.
Chris Lindquist up in San Jose who used to make up these parts as they are the same for the deluxe phaeton, 180-A, but I don't have a contact for him
The seat posts are a bit of a problem, the only ones I have found are available from A&L Parts, and they are close, but not the same as the originals.
Vern