For that classic, plastic sound, you can't beat nylon strings---cutting edge technology in 1955. The D'Addario J65 set sounds great on my Islander---I'm sure they'll sound sweet on your Ukette.
I'm wondering this very thing myself. I am considering using some Aquila iUke strings. Other people have mentioned thinking about trying it, but no one in this forum has followed up with a response about how well it worked.
I would like to try the Aquila iUke strings tuned up an octave, and/or Aquila reds - sopranino tuning - aDF#B.