Bunnings Cairns are clearing out a whole load of window hardware, not sure how much these locks used to go for at Bunnings but I've never seen a 4-pack of window locks go for less than $50 (sold elsewhere for around $55: http://www.supercheaphardware.com.au/sliding-aluminium-windo...).
They had about 10 or 12 4-packs left mid-afternoon today, most seemed to be keyed to only one or two codes. There was also a whole bunch of other window locks (singles and 4-packs) in other styles and colours available.
Of course, a real Ozbargainer would steal a whole bunch of dowel out of a skip and cut it down to fit the window track (cough cough) but after a few years Mrs Chickentaste was demanding a more elegant solution.