Two options - keep an eye on Abebooks for a second-hand copy, or go to this website: Symbols.com - Search which will cost you nothing.
I had the idea to buy Dictionary of Symbols and Imagery by De Vries, until I discovered that it costs 200 euros . Do you happen to know any cheaper alternatives?
Thanks for your help Anglika. About Symbols.com - Home, although it is a marvellous website, it's not what I'm looking for, as I'm mostly interested in symbolism and imagery in Literature, not symbols themselves.
Abebooks is also nice, I'll keep it in mind