Are you only using bleach? If so, then you can just add some CYA separately. But, you'll want to wait until your green pool is cleared up before adding it. (Is it any better, by the way?)

Go ahead and buy a 5 lb. container of CYA. It may be labeled as conditioner or stabilizer. Check the ingredients. If it says cyanuric or isocyanuric acid, it is the right stuff. You may not need all 5 lbs., though. Have you used any trichlor pucks this year or dichlor powder?