Thanks for all your suggestions! I've just been at my local electronics store and bought both a few 555's and a few BC547's, I'll experiment with both and see what I come up with!
@MarkT: Unfortunately they had no ICM7555. I was actually given ST SA555N. Are they any better than the original NE555's? I paid € 0,50 each. I also bought a few capacitors (0,60 each, not so cheap!), where would you recommend putting them with the SA555N? Oh, and the 10 uF I got are electrolytic, can I use these instead of the ceramic ones (which I thought were only in the pF range)?
@John_S: Very clever :): I'll try your trick, for curiosity's sake, but unfortunately I can't use it in the actual project, as I have no pins left at all.
@doughboy: I need two pins because the backlight is normally off and only gets switched on temporarily at the press of a button. So I need one input for the button and one output for the backlight.