How to tell what kind of meditation pillows i need for my stress-reducing exercise?

Ones in your mind: Seriously, medication is about your head, not what parephanalia you can buy or worry about buying. If one can only relax and meditate on brand x pillow, or type b pillow one has not developed the skill very well to find inner peace or reduce the stress from the real world. Any comfortable pillow will help, but i sure hope a certain type is not necessary, cheers!

Only if you want: You can sit on a chair for meditation, or use pillows if you like. If the latter, you want one that allows you to sit upright comfortably, with pelvis slightly tilted forward. This aligns your spine in its natural "s" curve, and opens your chest (heart) area. What you don't want is a "slouch" position that closes you back down. Really, though, a chair that supports you is fine also.