Yeah...if you don't have a Benjamin to spend on a twelve pack of em, or if you just like the DIY approach, try this:

I've found it's better to cut further into the T shirt at an angle so that the neck flap is deeper and the front that goes over your nose is the shoulder portion of the sleeve (avoids having the armpit seam rubbing on your nose).
I made a really nice one out of an XL/XXL polo shirt with the arm cuff cut off and rolled down and stitched around a piece of thin black elastic which comes out the back and is adjustable via a cordlock.
Or if you don't have any beat up T shirts, you can turn a T shirt inside out and into a "ninja mask"/headscarf...

Just saying...if you're broke, don't blow money on garbage Chinese face masks for any reason. You could probably even paint on a design if you really desired. I may paint a Cheshire cat grin onto my dark green one...