At least not for sale. The lumberyards and home stores seem to offer only hollow/flat, hollow/panel, and solid/panel wood versions. What is the reason you need or want a solid wood, flat bi-fold? Mostly Iím interested in why you need them to be solid.
Now my house does have solid/flat wood slider doors, but they were site-built. Iím fairly sure you would need to make your desired bi-folds yourself, as well, rather than being able to purchase them as a kit.