I've just returned from visiting the BIG ISLAND of Hawaii. I looked at a lot of maps of the island that were ok but simply lacked detail. I came across this one on Hawaii itself. It folds out so you can see the entire island on a big scale all at once. It has enough detail to get you around to all the towns and major gotta-see-that tourist sites -- many you never heard of. There are separate enlarged panels detailing Kailua-Kona and Hilo. This is the map I wish I had when planning my trip.
You can find this map at gas stations, tourist shops (ABC & Hilo Hatties), KTA grocery stores, every Long's Drugs and heaven only knows where else on the island. Or, if you want to really plan your trip in advance -- get it now. You'll be glad you did. Mark it up with pen, ink, magic marker, etc. It's cheap (buy two and you have one to frame) and will save you time navigating around the Big Island.
BTW, the paper must have improved since 2004 -- I folded and refolded this map a few dozen times and it's still intact. Combine this with the guide book "Hawaii The Big Island Revealed: The Ultimate Guidebook" and you're well on your way to planning a great vacation!
Aloha!