aussiegirl,
That's a nice little 99K, I really like the badge on it. I haven't seen one like that before.
You machine takes the common 15x1 needles and the Class 66 bobbins.
The plastic Class 66 bobbins will work just fine in it.
Here is someone you can contact right there in Australia that carries parts and supplies for old(er) sewing machines:
http://www.annebonnyslocker.com.au/ckp/a.main/index.htm
The gals name is Cyndy Kitt. I've done business with her and it went well.
For the rust I've used three things. White vinegar, Navel Jelly, and a product called Evapo-Rust.
I like the Evapo-Rust the best but I don't know if it's available in the AU.
Joe