Well you will have to find the drivers on a archive site since they are not on nVidia site anymore anyways.
Ahh it seems that they had 96.85 drivers out. They were RTM drivers
Windows Vista 64-bit RTM
But i can almost guarentee you that these drivers will be even worse than the current drivers. As these didnt have SLi support or work all that well. RTM drivers stunk from nVidia and ATi.
nvidia Vista drivers 64 Bit - Google Search
There is a google search that turned up a few sets. You will just have to test them for yourself.