I have always encountered this problem, especially when traveling. Of course, we cannot keep things in our traveling bag that, when we unpacked our bags, our shirts will be crumpled, right?! And there's nowhere to be found an iron, right?! One thing I do is to use my hair blower again!
Just hang your crumpled shirt, spray it with water and start blowing it with your hair blower! This is for an emergency situation, especially if you are going to a special occasion, like a wedding. So now there's no need to worry if you carry a wrinkled shirt.