I can' tell you anything about any brands, cause I have no experiance with any. But the ones that I have seen use the same filter technology developed from the people in the link below.
http://www.rainfresh.ca/productinfo/cartridges.html
The 1S & 1M, Silver impregnated, cleanable, reusable Ceramic Cartridge
* Traps and kills coliforms, faecal coliforms, E. coli
and other harmful bacteria > 99.99999%.
* Traps Cryptosporidium and Giardia (Beaver Fever)
cysts > 99.9%.
* Activated carbon core reduces chlorine, taste & odour.
* Filters sediment, rust, algae and silt as small as 0.3 microns
You can get these at your local home hardware. The only problem, the filters are for residential use, they are twice the size as one of those hand pumps. I supose you can cut it in half and glue a new fitting on the bottom.
CB.