Put this fgd code in the func_wall entity of your fgd:
style(choices) : "Texture Light Style" : 0 =
[
0 : "Normal"
-3 : "Grouped"
10 : "Fluorescent flicker"
2 : "Slow, strong pulse"
11 : "Slow pulse, noblack"
5 : "Gentle pulse"
1 : "Flicker A"
6 : "Flicker B"
3 : "Candle A"
7 : "Candle B"
8 : "Candle C"
4 : "Fast strobe"
9 : "Slow strobe"
12 : "Underwater"
]
Then in Hammer, make your light brush and func_wall it. Set the new Texture Light Style property to Grouped (-3) and give your brush a name.
Then place a point light entity. Set its color to 1 1 1 0.1 and put it somewhere where it can't be seen by the player. Give the light the same name the func_wall.
Now simply have a trigger target the light/func_wall. The light will now toggle on and off as well as the texture light as you keep triggering it.
Note that the light that the texturelight emits actually looks like as if it was just a point light entity. It won't look the same as how a static texturelight would emit light.