If you have a smartphone - doesn't matter what type - try the Copilot GPS app. It has an RV mode - set to 12ft 6in or 13 ft (even with a lower height Class B this is better than nothing) and also propane tunnel avoidance routing. The free version is full featured for 14 days and then limited but still usable. The Premium US version is on sale until Monday for $7.99 (usually $10) and has every feature a regular GPS has plus the RV mode - unlimited maps, free traffic for one year and then $10 per year. It loads the maps into phone memory so no data connection is needed for routing or traveling. Traffic alerts do require data but Rand McNally RV GPS for $400 needs data for traffic also. You won't be put on any low over pass routes any more and that is the best part. Try it for free and buy it if you like it.
Great catching that truck on video!