Got a set of these at Target (The Glen, 3150 Glen Waverley, VIC) on clearance. The tag said clearance $4 odd, reduced from $24.99, but they are having a 20% off sale on top of that, so my docket says $3.88
Says it fits bikes 30cm to 50cm.
They flip up tool free, with the pull of a lever/lock, perfect for when your little one is a bit more confident, or gets tired on a long ride.
Similar items can be found on eBay for $25 + shipping eg here…
http://cgi.ebay.com.au/140396986816
I found some very unfavourable reviews online but really people, if you don't know how to fit these properly,
please take it all to a bike shop and get them to do it!
http://www.amazon.com/Up-Down-Training-Wheels-Set/dp/B0015PD…
All said and done these are a damn sight sturdier than the ones that came with my sons $170 16" GT Mach1 Jr BMX.
There were still about 10 sets left earlier today.