Unfortunately, this filter has been discontinued by the manufacturer. There are no replacement filters available.
You can purchase a new faucet filter system:
http://www.waterfilters.net/Filters/faucetfilters/faucetsystems.htm
Or, if you don't want a system connected to your faucet, you could consider an under sink system such as the Culligan US-EZ-4 system:
http://www.waterfilters.net/Culligan-US-EZ-4-Under-Sink-Filter-System_p_0-434.html
Thank you,
WaterFilters.NET