An option might be to compile the driver yourself, X is modular now so it's pretty easy to just grab the tarball and unpack it (..or go into the ports tree and try manually updating the port).
The latest release is 2.1.15, FreeBSD appears to have 2.1.13.. and they don't have any FreeBSD specific patches.
http://cgit.freedesktop.org/xorg/dri...o-nv/refs/tags