We are in the foam-age of model flying. However, some stubborn enthusiasts still prefer to build their own models.
Unfortunately, it is not so easy, and expensive, to get balsa and plywood.
There is one big exception: Balsacentral, a distributor in South Australia, also retails online, and at half the prices when compared to the model shops.
They sell basswood ply sheets, balsa squares, shapes, sticks, sheets, and blocks in various sizes.