https://www.cincinnatidowel.com/dowels/3-x-30-wood-dowels.html
Large Diameter 3" Diameter Dowel Rods - Maple https://www.amazon.com/dp/B001PKLUUS/ref=cm_sw_r_cp_api_i_Vf3cFb6AZ0WQD
https://www.rockler.com/large-diameter-dowel-rods-3-dia