Mods drop as random on weapons. If you want scythe mods, for example, go farm Dervish mobs and idenfy purple, blue ja gold scythes and hope for mods. Might be easier to farm cash and buy the mod.
I think the best place to farm weapon mods in general is the Raptor Nestling cave. I've picked up a couple of zealous scythe mods (amongst many others like sundering, furious, 15^50 inscriptions etc) along with a couple of snazzy looking Saurian Scythes from chest drops.
If you're specifically after a decent zealous scythe you can farm Asterius the Mighty outside Olafstead for his scythe. I do runs there for norn title points and have picked up a few of his greens.
Last edited by Antithesis; Dec 22, 2007 at 10:51 PM // 22:51..