I like an L1 surefire. The low beam is useful for checking out what the pooch is doing in the shadows - without waking up the neighborhood. The high should be OK when crossing the street. It has a pushbutton/twistie. A slight push turns on low, and a stronger push gets it to high.
I don't think that you should have to blind the drivers to get their attention, at least in my neighborhood. It is pretty dark here at night - no streetlights. The L1 seems to be fine for this.
I add an FO4 beamshaper to make it a flood, but you don't really need to for signalling.