I asked the same question a fair few weeks ago.
daveh75 replied and recommended this
http://redirectingat.com/?id=1044X500158&xs=1&url=http%3A%2F%2Fwww.audiovisualonline.co.uk%2Fdynamic%2Feshop_products.set%2Fref%2F3419%2Ffisual-mini-toslink-to-standard-toslink-cable-pro-install-series%2Fdisplay.html%3Futm_source%3DFroogle%26utm_medium%3DFroogle%26utm_content%3DMJI%26utm_campaign%3DFroogle&sref=http%3A%2F%2Fwww.whathifi.com%2Fforum%2Faccessories%2Fchord-atlas-co-axial-toslink-thing-apple-airport-exp
Was really cheap , does an excellent job and is well made. The service from the supplier was also excellent. Just make sure you order the 2m one ( I ordered the 1m due to the 2m being out of stock and it could do with that little bit more length ).
daveh75 is a guy in the know and said you dont really need to spend anymore in his opinion and I totally agree having now got this lead.
Its on page 3 of this forum if you want to have a look at the post ( under toslink thing ).