You don't need one. Three of the pins on the CPU fan connector are in the same configuration as a standard, 3-pin male fan connector (see the pinout diagram on pg. 2-7 of your manual), so a standard 3-pin female fan connector with tach lead will plug right on. You only need a 4-pin connector if your HSF comes with a fan that has one (the fourth wire is for fan control). So for a normal HSF the 4th pin will be left unused.
.bh.