I've been looking for one myself for over a year now. I've seen 1-2 on ebay, but I missed them. A boxed Legendary Axe, turbo link, TE AC adapter went for $15 a few months ago. I was "watching" the auction, but forgot to bid! Godammit! I thought I bid on it! Goddammit!
I don't know how high the auction would have gone, and I only needed the turbolink, but still....
Maybe someone here wants to sell you and I some of the extra TurboLinks they have lying around!
From what I remember (I owned a TurboLink back in the day but lost it at some point), it was equivalent to a mono 1/8" (or was it 1/16", you can test it on your TurboExpress) male jack. Both ends of the cable had the male jack. I never tried using a generic cable, but I've always suspected that it would work fine.
If anyone can confirm my suspicions, it would be greatly appreciated.