Dave wrote Does anyone have a 5 speed Cyclo rear derailleur that they'd be willing to part with?
Just to add to other answers to your requeat Cyclo did not manufacture a
5 speed rear mech or sprockets of that number. They did have two models
at 4 speed namely Cyclo Four Speed a pulley type with top tube double
cable lever and Super Olympic either in 3 or four controlled by the
conventional down tube lever.
Hope this helps