Recent thread on reddit.baduk lead me to this dealer. Exploring similar products and listings led to several other antique and wholesale outfits, opportunities for low cost floor boards in all conditions, from pristine to thoroughly messed up, and a weirdly wide price range, from under $200 to $10,000.
This particular guy has several sub-$500 floor boards, some with stones. Shipping by slow boat runs about $150-200. This post will be out of date soon as his inventory will have changed.
https://www.ebay.com/sch/abarebugyo/