With Sofnolime I use filters from the hardware store.
Filters:
AOSafety "COOLMAX" the # 1052 is printed on the front of the filter. The # 95014 is printed at the top of the packaging. They're pleated rectangular filters. Trim the edge off the entire filter and you're left with 2 pieces of material that are remarkably similar to the Inspiro filters. Use the KISS scrubber cap as a template to cut slightly oversized circles. Place them on the scrubber cannister opening and work the edges in with a flat blade screwdriver... Voila! They work great and seem quite durable. Cost is $6.00 for two and you get enough material for at least 4 filters.
The company that produces them is AEARO Here is the web address (long, add both lines):
http://www.aosafety.com/diy/project_...bproject_id=18