You're absolutely right - I got confused between Mike's photo and the OP.
One thing I've done on a couple of kids bikes is to use a front derailleur, like in the photo, but crimp it in a little. Obviously this ruins the front derailleur but it's not hard to find a cheap old unit to sacrifice.
Shortening the chain really makes a difference in my experience. I've got an old MTB I've converted to 1x, and rarely drop the chain. I fitted a narrow-wide chainring and am running the chain quite short.
Any chance you'd be willing to post this to Sydney, Australia Ducky?
I've picked up an early 9s Shamal and thought I had a spare 26mm lock ring for it but can't find it!
Looks like it could go as a "large letter" and postage wouldn't be too bad.