There are a number of things that are used in the bottom of cages and flights, from bird sand to sawdust and even paper, which I would not advise, even though most inks used today are said to be safe, it's not a chance I would take.

What we use is Easi Bed, this is a horse bedding very its absorbent not too light, and great for the Kakariki to do their natural scratching about in. it come in bale size bags so goes a long way. It cost is somewhere between £6-8 a bag depending on suppliers. you can find your nearest stockist by using this link http://easibedding.co.uk/easibed/