In 12.10 this method works without installing any additional themes.
Two changes to make.
Set the cursor size in dconf.
Where xx is your cursor size.Code:gsettings set org.gnome.desktop.interface cursor-size xx
Default is 24.
Use 16, 32, 48, or 64.
and add or edit the lineCode:gedit ~/.Xresources
using the same value you used for dconf.Code:Xcursor.size:xx
Need to reboot.