They aren't that hard to find, you should find them at a Best Buy or radio shack. Give them a call first and make sure they know what you want, because BNC can refer to network cabling connectors.
It does help out with clarity. I couldn't use any resolution over 1280x1024@85hz since it was fuzzy , BNC has higher bandwidth and now I can run at 2048x1536 crystal clear sharp text. THis should probably help in games too, at high res.
Colors are slightly more vibrant too.