Camping World sells a "T" fitting, which installs in lieu of the traditional vent camp ... which works the same ... but only when you are running down the road (because it's fixed and doesn't swivel).
The "weather-vane" feature of this would seem to allow the device to work while camped ...
But I gotta tell you ... I just can't imagine that this device can withstand the rigors of 1,000s of miles of expressway travel, with crosswinds, and suction winds from passing semi tractor trailers, while Charles II is driving 75 mph.
Might be the kind of thing you could install while camping and then remove for road travel.
Forgive me for asking, but are you having "odor" problems with your toilet?
What kind of chemicals are you using?
We have had years and years and years of success using Bob Steffen's home brewed pinesol mixture.