Not all the sellers that describe their products in details and when they does it's often over-priced!
A good S-Video cable for video deliver 75 ohm impedance and have multi-layers protections (coax RG-6 like)
And it's always good to shop. I recently buy a Acoustic Research MS-2200 master serie.
They are huge and have all the specs needed. But prices varie a lot. I got mine for 3.95$
But I found this site that seem to have good quality at cheap price
KHX S-Video Kable
And also S-video.com
have many S-video accessories.
That the information I wanna share...if you know others sites...just share them!