The most recognizable image of an astronaut is the spacesuit for extravehicular activity. It's the kind of thing that looks more like a vehicle than clothing: with a rigid frame, a cooling loop, and a flashlight. That's what we're going to draw.
First β the helmet. It's rigidly fixed to the torso, and the astronaut's head moves inside it, which is why the helmet has a huge visor protected from the sun.
Next β the cuirass, to which the arms and the lower part of the torso are attached. And on the back β a massive box housing the life support system and other useful things.
Doesn't look very comfortable, but out in open space, you simply can't do without all of it.