There is the new SureFire SRxx Dual Function Tape Switch with Rail Clip
(where xx is the length of the cable in whole inches, for example
SR07 (7" long cable)
This features a momentary-on pressure pad section and an integral constant-on/off pushbutton click switch. The tape switch features a snap-on clamp for quick attachment to your picatinny rail forend.
It plugs into the XM, UM or UE (ScoutLight) TailCaps.
The XMxx and UExx TailCaps come with a momentary-on tape pressure switch at the end of a cable length xx whole inches.
The XM/UM/UE TailCaps can not be ordered with the new SRxx dual function tape switch. You need to order the TailCap by itself - To order just the TailCap (without a tape pressure switch) you need the XM00, UM00 or UE00, and the SRxx you want as well.
I believe the SRxx is in the process of being released but may be difficult to get hold of.
Al