I'm sure you could find some real cheap ones, but do you really want to risk the water your putting in your tank for a couple of dollars? I'd consider joining a group buy on BRS, and buying their replacement kits, or getting a coupon for other reputable stores, instead of just looking for the cheapest. You may save a few bucks buying some cheaper knock offs, but if they don't do the job as well, your going to spend a lot more trying to fix the issues that your tank will have. Just wanted to try and help you avoid any headaches in the future. Good luck!