Is there any method or mod that can be used to give this game a vsync option?

You can use a third-party program to do it. Details at the bottom of this post:

http://www.gog.com/forum/the_witcher/fixes_to_common_problems/post1

Yes, you can create a profile for the game in your graphics card configuration program.

As example, for a nvidia card, right click in the desktop, select NVIDIA control panel, control 3D settings, here go to program settings tab, select The Witcher for the list, now find vsync option in the list below and change use globlal settings to enabled.

For ATI card is similar.

Note, I have the nvidia control panel in Spanish, so is possible that the options are not named exactly as I transtaled them.

I have an ATI card and I was unable to force vsync in my graphics drivers as you suggest. It works for other games but did not work for the Witcher. However, I was able to get vsync working using D3DOverrider, as I suggested above.

It's worth trying the graphics drivers but if it doesn't work, give D3DOverrider a shot.

I use SweetFX, you can find some good settings if you do a search.

I don't think it does VSync, but it does some very nice AA and other post-processing stuff.

I also use it for The Witcher 2, because the Ubersampling drops my FPS, and SweetFX is looks just as good to me, but without the slowdown.

If you have an intel laptop like me, look at the lower left corner near the clock, click on the arrow pointing up, then find the graphics adapter, right click, properties, and you can set vsync on there