garmin also do one ,its the Nuvi 465THi Reg I have not used any of the sat navs designed for HGV's or caravans,but I have read that they do not actually plan a route around possible dodgy roads/obstructions,but place a warning of an obstruction/road restricton,on the planned route in the form of a POI.You then have to plan a route round the obstruction,or ask the unit to reroute you if it would cause you a problem
I mention this as it may be another point to investigate before you buy