Go to menards, hardware section, they have high quality respirators for 20-30 dollars depending on model and purpose. Mine is for organic vapors, and it only cost 21 dollars, plus cartridges were only like 15 dollars for a pair.
Dont go looking for cheap quality cheap priced mask, know where to find good mask for a good price.
Spending the extra 5-6 dollars is better than spending 5000 dollars at the hospital for your lung problems.