Flash for Olympus 35 SP

[torokoh]

Hi! I've just got my first rangefinder camera; the Olympus 35 SP. In fact, its just my 2nd camera (the 1st being a Samsung P&S). I am hoping to get some advice on what type of flash unit will be suitable for the camera so that I can shoot at night. The original Olympus PS100 flash unit seems to be very rare and expensive if found.