Hi Chris,
indeed Steib made very nice models and there is a shop in Berlin making them new, also "lefties", but not very cheap.
i had several in my life, the lightest is model LS200, but model S250 may be of better shape to fit the Dragonfly "modern style".
I must agree Eddie, there are no specifications on the Fly to attach a sidecar and I´m a bit sceptical to do it.
Michael