Try a different sized Berkey including the Berkey Light. I think people are concerned again and buying stuff up.
Prefilter outdoor water thru coffee filter paper. 1 lb. of the right pool Shock will disinfect 9-10,000 gallons of water and cost you a few dollars.
PS: Read up on the Berkey Sport -- I do not believe it is nearly as effective or safe as regular Berkey filters but not sure anymore. I am a fan of Seychelle Advanced water straws as a short-term but compact and light, easy to use, incredibly effective, item. Think Get Home Bag, BOB, etc.