to NGA
Have you gone to places that have rain barrels and asked if they would donate one? Sometimes its good (for them) for free advertising.
Use your imagination for some other options:
My daughter made a rain barrel out of an old 55 gallon food grade liquids drum (her's contained fruit juice). She plumbed it for a faucet at the bottom.
Daughter #2 made one out of an old water trough - she just bails.
My girlfriend built a pond that she can pump water out of. An above ground cistern! She never pumps all the water out - the fish would hate that.
Daisy
