The Fostex COP-1 and a Core Sounds both can change optical to TOSlink and vice versa. Both cost about $100US, but they are different enough that probably one or the other would be a better use of money depending on your needs.
The Fostex is a two-channel device. It converts a coax in to a TOSlink out, and a TOSlink in to a coax out. Both are active at the same time. There are no operating controls on the Fostex. Ideal if you are already set up to deal with coax (or TOSlink) and want to set up a deck with full time digital ins and outs.
The Core Sounds is a one-channel device. It has two inputs, one coax and one TOSlink. A switch chooses which is active at any given moment. It has two outputs, one coax and one TOSlink. Both outputs are active at all times. Better if you want to multiply a single input to two devices (one coax and one TOSlink) at the same time.
So as they says, you pays your money and you takes your choices. A short drive with a soldering iron will save you a bunch of bucks, but that wasn't the question.
Fostex is widely available. The DAT Store is one place among many others. Core Sounds is available only from Len Moskowitz's Core Sounds. It would be better to get the Fostex in Austrailia because of the mains difference. With Len's box you will probably have to obtain a wall wart locally.