Check out Vanness for your Pencil Lead needs.  When selecting pencil lead, Check your mechanical pencil for the correct size. 

Press the filter button above to select the size you need. 

Other things to look for is the hardness levels. The most common are 2B, B,HB, H, and 2H  these are listed in order from Softest to Hardest with HB is  the middle of the pack for both.