[aerohead]

I've seen one published Cd for an RV travel trailer since 1974. And it wasn't a 'teardrop.' This trailer was depicted, being towed by a Honda Accord, and there was no attribution specificity as to whether their Cd was ,measured as a tow vehicle/trailer 'system', or as the trailer in a wind tunnel by itself. No 'context', no 'conditions.' No 'actionable' information.
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Wolf Hucho's 2nd edition,' Aerodynamics of Road Vehicles' is the 'richest' single source for trailer data I've seen.
And the 'trailer' discussions here at EcoModder include all of it, plus everything published in the public domain, flagged by members over the decades.
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As to 'teardrop' trailers:
Baron Reinhard von Fachsenfeld personally measured the drag of a 'solo' structure which closely resembles the architecture of 'classic' teardrop trailers, recording Cd 0.45, at either Braunschwieg Technical University, or at Dr. Kamm's, FKFS, next door to Daimler-Benz, in Stuttgart.
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Such a Cd is 'useless', divorced from the effects of the tow vehicle ahead of it.
And since there's an 'infinite' number of potential TVs, along with an 'infinite' number of RVs, it would bankrupt a manufacturer attempting to 'cover the entire field' of combinations.
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All we can do is to compare 'solo' mpg of a TV, to it's mpg while towing a specific TT, then overlaying the frontal area footprints of the two, together, come up with an AF of the 'system,' plus it's all-up weight; then calculate the increased rolling-resistance, factoring that into the energy balance for the 'rig, allowing a constant BSFC, or BSFC-e for the tow vehicle.
From this, the Cd, and CdA of the 'rig' will fall out from the math.
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Just calculating the frontal area of an 'Airstream', 'Argossy', 'Casita' ,'Happy Camper', etc. can set you back half a day.