You might could find the activated charcoal in pet supply stores, where it is used in aquariums.
It's most likely activated carbon, which is the same as activated charcoal. For your purpose, it will have to be food-grade. A water-conditioning store sounds like the best place to find it.
We have our own water distiller and it has a small charcoal filter in it and I ran into the same problem with the filters being so expensive. I found out the top came easily off the filter and had probably the same charcoal you are talking about. I found that they sell the charcoal in water conditioning stores. I paid @ 5.00 for a container that will last at least a year. Quite a savings. I don't know what the bags you are talking about, but I'm sure you could refill them or make some. Call a few stores in your area, for the charcoal.
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