Theres a story about the Montesa 50 kids trials bike in Australia. The Aussie importer thought there was a market for them with Australia Post as postie bikes so they imported some (10 or 20, I can't remember) for Australia Post to evaluate. The bikes that come up for sale now and then in Australia are probably from that batch.
A kids trials bike that was actually used for a serious purpose was the big-wheel TY80 Yamaha. At Queensland Alumina in Gladstone, Queeensland, there were lots bought and used for on-plant transport, so there have been lots of them around here ridden by kids ever since, after they were sold off by QAL.
As well as the TY80s, QAL bought lots of Honda CT110s and TS185ERs.
At my current workplace (Gladstone Power Station), we recently sold off our fleet of aging XL100s (red and black 1979 model?) that had been used for on-plant transport since new.