The best way to get solid wood thicker than 2" is to glue it up and mill it down to the size you need. Believe it or not, this is more common than you might realize. Thick hardwood lumber is quite uncommon for two reasons:
It's hard to dry thick lumber; the drying process results in a lot of waste and degrade in thicker lumber. This makes it expensive and rare.
Low market demand
Glue up your own thick material when you need it thicker than 2". It will be more stable and you can get exactly what you want this way.
We do carry a few hardwood species in 12/4 or 16/4 such as Hard Maple, Poplar, Basswood, Walnut, or Honduran Mahogany. Please call or come in to verify what we may have in stock at the time.