How about a...
"7-pin S-Video plug to 4-pin S-Video jack adapter"
I only found one at
this website (svideo.com).
Please note I have
NEVER heard of this company, so it may be wise to look elsewhere. I cannot find any ratings of this company, and I would NOT recommend buying unless you find some positive ratings.
It may be easier to call up the manufacturer of your video card and ask if you can purchase the part. (In fact, I'd do that first)
- rp