Derek at Urban Offroad does reproduction rear ladder sections (and entire backets set ups as well).
I am sure he could also provide you some supports that ran from the front cross bars to the rear ladder that could provide stability for hauling the items you refer to without requiring a basket being attached.
He did my entire set up, cross bars, basket and rear ladders.
He does good work. May be slow to respond to an e-mail, but does good work.