I got mine from America, just shop around the Buick, Chrysler GM online stores for best price with P&P and Tax (I paid about £125 for the 3 chains, 3 sliders and 3 tensioners delivered IIRC). Problem is they take about a fortnight to the UK so no idea to SA. You may be better looking at Holden/GM sites in Australia for Southern hemisphere parts!
There's 3 chains in total but not sure if your car is early or late type, they may have changed around 2008. You may as well get new sliders and tensioners whilst you're at it. My sprockets were fine so didn't change them. I've got a set of later Morse style chains (bought by mistake - doh!) if you have a later engine but no idea how much it would cost to get them to SA.
If you need GM part numbers let me know and I'll try to dig them out.