Directions? Stargazer? But (and this goes for manic panic too), they stain everything they come in touch with including your skin, fabrics, pillow etc. The best I've used is the Fudge paintbox range. Your best bet will be eBay. All of these all semi-permanent and you will only achieve bright results if you have light hair or if you bleach your hair first.
beeunique.co.uk delivers worldwide quite cheaply. The best dye they have is special effects - lasts about 3 weeks even if you wash your hair every day and the colours are really really bright! Expensive but totally worth it. (I've been using them for a couple of years now - ask me if you have any other questions!)
I've tried Stargazer which was rubbish, and Directions, which was fantastic. My green hair lasted months with no touch up, and when it did fade it faded really nicely to a good shade of green, rather than a skanky colour.