Rowenta RS-DG0123 Knob Trigger, Blue
Carefully pry off blue handle cover on top with a popsicle stick.
A quick (maybe permanent) fix while waiting for your part: you can "weld" the plastic trigger back together. It doesn't have enough surface area for glue. Position the break back together. Secure parts so they don't move. Heat a medium-small flat blade screwdriver until it will just
melt the plastic with a gentle touch. Touch the tip parallel to the break and melt a shallow groove about 1/4 of the way into the break. You should be centered on the break so you melt a bit of each piece. This will be the start of melting the two pieces together. Now, as you do each side of the break, use the flat of the blade to "trowel" the curled up plastic back into the groove you just made. Be careful not to distort the side that activates the switch. Ours is holding so well that I keep the new part in case this ever breaks again.
Less is more: use only enough heat to melt the plastic with a gentle touch. If it's red-hot you went WAY too far. You can always try more heat, but if you fry the part, you are done until your new part comes.