Looking for thinner FJPP in 8" widths and long lengths

Hi all, I am matching paint grade baseboards in a 120 year old house. It has some plaster, some drywall, all placed on top of 4/4 baseboards. I'm trimming out new walls from a remodel.

I'm trying to match the exposures of the top of the baseboard in each room. They range from 3/8" to 5/8". Thus far I have needed short pieces and have been using AC or BB plywood, or Azek (near tubs or showers). But now I need long lengths.

I was hoping to buy 8" wide FJPP baseboards (9/16") and plane as needed. But my suppliers are saying they can't get 8".

Any options other than buying 1x8 material and planing it?

Random picture, for attention.