I started trawling TradeMe (New Zealand's too small for Ebay to bother) and ran into a problem. New Zealand seems to be going through a Ukulele renaissance at the moment and second hand ukuleles are going for hundreds of dollars while guitars are going for tens.
Would it be possible to take 2 strings off a guitar and call it a ukulele?
Step 1: Find the Right Scale Toy Guitar
Since you can't pick up and strum instruments online, it's always a gamble, but at least you can find out whether it would be possible to string it as a ukulele.
Here are some typical ukulele lengths. I know I found them online somewhere but I can't remember where. Scale Length (SL) is the distance of the strings, from nut to bridge (see photos). Overall Length (OL) isn't as important as scale length but it is more likely to be in the description.
Soprano Uke - SL = 13"/33cm OL = 21"/53cm
Concert Uke - SL = 15"/38cm OL = 23"/58cm
Tenor Uke - SL = 17"/43cm OL = 26"/66cm
Baritone Uke - SL = 19"/48cm OL = 30"/76cm
The toy guitar I found was:
SL = 49cm OL = 74cm so I was confident it would be OK for a baritone uke. It also had two missing tuning pegs which didn't bother me but is probably why it went for only $10.