My tools are all disorganized at the moment, but if you're dealing with a variety of equipment, you'll definitely need both a metric set of Allen wrenches and an "English" (fractions-of-an-inch) set. Most hardware stores have them for only a few bucks.
I'll post again later if I find my sets before anyone else posts the actual answer; I think I still have a PS-2 that I haven't removed the belt clip from.
--best regards