Use any "modern" derailleur (like this type)
on any bike with long dropouts (like we were discussing)
Really, though, you can craft one from a piece of aluminum or thin steel flat stock. I made one of aluminum before, and the bolt on the derailer was hard enough to cut threads in it. It worked fine but flexed a little when cross chaining heavily on a 20" bike.
Ebike stop is good company, they have the fancy "emergency hanger" $13. I've bought from them before, fast shipping.
Here's another emergency hanger that gives some adjustment $15
Originally Posted by 5-7HEAVEN
Ibedayank, The Aleman and happycheapskate.....
The bike looks ALMOST exactly like Ibedayank's pic, except there are cable guides under the length of the down tube.
I am glad that there is an adaptor available to hang a good-quality 7-speed derailleur. I'll definitely get that piece!