Hi Clifford,

In Oz the source used to be RJ & US IMPORTS
http://users.catchnet.com.au/~rjandusimports/

But they have ceased trading, although there's still lots of info on
their site.

I think now the best local source is
http://www.minikits.com.au/products.html#ferrites

In the USA, try "The Toroid King" at
http://www.partsandkits.com/

But these days I usually just look an ebay for any radio bits and pieces.

Regards ........ Zim ....... VK3GJZ