The patch is available aswell as the patched source (which may or may not work for you).
Usage - Copy the source or patch to /usr/src/usr.sbin/moused. If you got the patch, then do patch < moused-patch. Run make all install and it should build it and install it for you.
Two new options are thus added to your moused: -V and -U. -V enables virtual scrolling and -U with a number parameters specifies the distance threshold (defaults to 5) before a scroll tick happens.