Just get one made - i'm sure you have access to some good potters.... i'd even bet that a large number of fermentation-crocks are made in africa then shipped to europe... :)
Alternatively you can get the required air-locks at a beer or wine brewing place.
Lid with water lock for most size glass jars 1gal / 2gal
glass weights for submerging fermenting food
For ideas and alternatives - http://www.culturesforhealth.com/natural-fermentation/fermentation-crocks.html
Just remember to keep these in a dark place - sunlight isn't good for them.