You can get nice expensive kits from the likes of Grace (american) from Henry Krank or online auction sites, but the best screwdriver bits are the hollow ground profile (so curved profile when looked at side on) hex type - I've found the Lidl sets excellent quality and their bits don't break easily and they are good value - a set is well under a tenner and will have pretty well all the sizes you'd ever need. This profile is less likely to slip and chew up screw heads.
Punches are best made from brass as steel risks damaging the gun parts.
In terms of mallet, a small brass or nylon/nylon & rawhide/copper & rawhide will do nicely. Thor are a good brand.
Most tool shops, machine mart, halfords, t'bay etc will have them.