I hate to admit it but I've never been inside a TH nor have I looked inside one other than in passing so I may not be one to listen to. There are a huge number of pull down and Murphy bed mechinisms available but not necessarily within the RV industry.
Most will be from places like Rockler Woodworker stores and from wholesale furniture suppliers. I have seen spring loaded pull down bed frames and fold up frames. It seems that Europeans are more likely to have these things available than here. Simplicity is also a key feature of their lives.
Most of us are familiar with the industrial uses of Cotter Pins but few know that the inventer of the Cotter Key(not pin)), did so for the European knock down furniture industry, back in the 1800's. You'll probably find your answer someplace other than a RV supply store.
"I travel not to go anywhere, but to go. I travel for travel's sake. The great affair is to go". R. L. Stevenson
David Bishop
2002 Winnebago Adventurer 32V
2009 GMC Canyon
Roadmaster 5000
BrakeBuddy Classic II