http://www.faucetdirect.com/kitchen/c1
ここなどどうでしょう。
Watts Premier 500023 WP-5 Reverse Osmosis System
https://www.wattspremier.com/products.php?product=Watts-Premier-500023-WP%252d5-Reverse-Osmosis-System
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dtools&field-keywords=Watts+Premier&rh=n%3A228013%2Ck%3AWatts+Premier
こちらで探すのはどうでしょうか。