In case you didn't catch my reply before some of the posts were deleted, it's in the Book of Eldritch Might.
Scabbard of Venoms: This black leather scabbard fits any longsword or short sword (it grows or shrinks as needed). A blade sheathed in this scabbard, when removed, is coated with a single dose of a poison that inflicts 1d4 points of temporary Constitution damage, and 1d4 more a minute later (Fortitude save [DC 16]). The scabbard can produce only 10 doses of poison each day.
Caster Level: 7th; Prerequisites: Craft Wondrous Item, poison; Market Price: 5,000 gp; Weight: 1 lb.