your best bet is to get second hand or e-gay...
to replace them is easy enough.
now I don't know how much detail you need so just go with the flow.
1. Loosen wheel nuts
2. Jack up car
3. Put a safety jack or bricks under chasis to support
4. Remove wheel
5. Remove Brake calipar
6. Remove floating disc rotor
7. spin wheel, so that you can see more of the back of the king pin.
8. if it has abs, remove the little abs probe, small 8 mm socket (from memory)
9. remove the 4 alan key bolts, if they are stubborn(as they have loctite) give them a tap with a hammer it will loosen the threads, (careful not to damage the head of the bolt, so a block of wood or brass hammer is the go.)
10. to fit reverse the order.
hope this helps.
if your in Adelaide I have one or two spare here.
pm' me if interested, I can send them over for a good price.