Legally, over the counter, while In Town you can purchase any item from the Basic Set equipment list, from the tech level as specified in Dungeon Fantasy I.
As a rule of thumb, this is any TL3/TL4 item that is appropriate for a D&D-esque fantasy world.
One Eyed Ike's is an archery specialist store, supplying delvers and militia alike with bows, crossbows, slings, arrows, quarrels, and reasonably sized rocks.
Crazy Ahmed's Used Weapon Hut specialises in slightly damaged items of all sorts, where, if you don't mind a few bloodstains, you can get all manner of cheap weapons. Even better, they'll *pay* for nicked and damaged stuff, and not ask too many questions about where the original owner is.