I would like to make some at school with the pupils.
It's just as easy to start it from scratch with bakers yeast:
Grow your Ginger Beer Plant with 2 oz Baker’s yeast (buy at a bakers). Put the yeast into a jar and add half a pint of water, two level teaspoons of sugar and two level teaspoons of ground ginger.
Feed it each day for the next seven to ten days. by adding one teaspoon of sugar and one teaspoon of ground ginger. The ‘plant’ will grow each day.
Strain the mixture through a piece of muslin or fine household sieve (keep the sediment), and add the juice of two lemons, 1 lb granulated sugar and 1 pint boiling water. Stir until the sugar is dissolved then make up to one gallon with cold water.
Bottle the ginger beer, filling the bottles to about 3 inches from the top, and leave for two hours, take care not to put them on a stone floor, unless standing on a piece of wood. After two hours cork lightly. Keep for seven to ten days before drinking.
And now you can start again. The sediment left when you strained the liquid is divided in half and put into separate jars. This is the ‘yeast’ starter and you can begin the recipe again, with “To your recipe add half a pint of cold water …..” Don’t forget to give a friend the other half of the ‘starter’, and a copy of the recipe!