There was one available, but I don't know if they have been discontinued.
They were available at the sandwich shoppe. It requires you to mod the original momentary tailcap though. The two stage offered options for selecting resistors for different low-level outputs. I own two of these and love them in my lego'd C series Surefire lights. They are very hard to come by now it seems, but maybe a request in the BST or the Marketplace will help you find one.
I forgot to mention that these were only for LED modules.