What you are looking for is plywood veneer, used by furniture makers to make pine look like oak etc. Just ask a furniture maker/ factory if they'll sell you some or let you rummage in their bins for scraps! I use the stuff to make weatherboard houses and shingle roofs. I'm just completing an AWI church at present.
Hope that helps.
Alternatley you could buy 3mm ply sheets and let them soak for a month, dry our, soak again etc until they start to delaminate.