This is what my husband has used in the past. $18 for the regular version, just under $55 for the spiral-bound laminated version.
For your own comfort, you may want to actually measure your rig at its tallest place. That would mean where the A/C, satellite dish (travel position), MaxxAire, or whatever is tallest. Frankly, only in national parks did we run into any low-clearance areas, and they were well marked with usually a detour to go around.
We were more impacted by a couple of other things. One was a place located on private property, where the grade was not well done. The cabover portion of our 5W collided with the truck's tool box at that point. Ouch, but thankfully, no real damage was done. Another were tunnels. You may be routed away from certain tunnels because you are towing with 2 propane bottles (as are most RV's). Fortunately, these are even few and far between. However, the trucker's atlas made a note of these, too.
Donna