If you are after a flow control tap but already own a tap and shank then this is what you are after.
 
Just remove your tap from the shank and add the Flow Control Shank Adaptor in between the shank and tap* to turn your tap into a flow control tap (will fit most shanks). 

This part comes with an Allen Key to tighten the grub screw which enables you to lock the flow control into position to make it so you don't need to worry about anyone changing it on you.
 
*Note: THIS PRODUCT IS NOT COMPATIBLE WITH ULTRATAP VARIETY FAUCETS. The Flow Control Shank Adaptor does not include the Tap or Shank