Purchasing Doulton ceramic replacement filters

I do not see a web page for simply purchasing replacement filters. I would be interested in the carbon block candle style pB1 (with lead reduction) filter and the Sterasyl candle (in the event I decide to buy the IP200pBS).
The IP200pBS is very similar to IP100UC with the exceptions that the 200 model have a 1 micron carbon cartridge as a pre-filter with Sterasyl candle as a final microbial protection. The Ultracarb have both filters into one ceramic shell. The only advantage is that Sterasyl candle can be cleaned over 50 times however the carbon filter have to be changed every 600 gallons or 6-9 months and it's a bit less expensive than Ultracarb . To ensure the carbon chemical effectiveness we recommend Ultracarb change out every 6-9 months regardless that the ceramic shell is still effective for microbial protection. The candles can be purchased at the following link. http://doultonusa.com/HTML%20pages/ceramic_candles.htm