Evaporative coolers - cartridge renewal

Mr_S_in_Easton

I have a small evaporative cooler, which is really useful in this hot weather. OK, its not like having full blown air con, but its modestly effective when next to the bed, very quiet when on the lowest setting and keeps my head & torso cool enough to make a real difference during these hot sticky nights. My Q is about the paper element which soaks up the water to cool the air when its running. The makers (Evapolar) suggest it should be renewed periodically, and offer spares at about £40 a pop. I wonder why they need renewing and given that its only a simple folded paper element, has anyone sourced these from alternative suppliers at more reasonable cost?