Razorback's correct. It's in Volume I of the TBB on page 91 of the "Bow Design and Performance" chapter. Here is a direct quote:
"If there are no trees in your town, and no hardwood lumberyards, puck up a rake, broom, or hoe handle at the hardware store. The longer, thicker, and more straight-grained the better. The larger diameter handles make up to 40 lb bow. Hickory pick handles [like those picture] can be spliced together to make a first-class, high weight longbow or flatbow."
Good luck, and post some pictures!