Apple Pro Speakers Minijack Plug to 3.5mm???????

I would love any suggestions anyone has as to making Griffin's Pro Speaker Breakout Cable compatible with the iMac G5.

I just made the very foolish mistake of purchasing Griffin's Pro Speaker Breakout Cable for my iMac G5, which I am sure others, more up to speed on their apple products, realize are not compatible. The Pro Speaker Breakout Cable, as its name would suggest, connects to the Apple Pro Speakers Minijack available in G4s and G3s.

I need someway to connect this Apple Pro Mini plug (2.5mm plug) to my audio-out 3.5mm output jack on my iMac. I have found this connector http://www.mpja.com/productview.asp?product=11298+AD but I am not sure if the 2.5mm Apple jack is the same as other 2.5mm jacks. Does anyone know if the two are compatible???

I guess the other option is the iFire - or, conversely, to just forget the whole thing and get some new speakers.

Any suggestions on the best/ most cost effective option would be greatly appreciated!!!

Thanks in advance,
Chris