The item number for the carbon filter for your coffee maker with model number 249401, 249402 or KZ-1228 is XX-122805E.
This filter is sold by piece.
This can be ordered through following link
The filters are mainly for eliminating any taste that may be present in the water by using additives to purify the drinking water. The carbon filters neutralise any aftertaste. However, it is possible you will not notice the difference.
If you do not use them, it is not a big problem and they will not harm your coffee machine either.
This solution is valid for the coffee makers 249401, 249402, KZ-1228