A highly dense and mildly poisonous metal, lead is used mainly for making radiation-resistant armor mods as well as chemical substances such as Mentats and the Lock Joint syringe at the chemistry station. Lead is also used to make most of the ammunitions through the ammunition plant.
Shipment of 25 units
A large supply of lead items can be found in Madden's gym at General Atomics Galleria. Be warned, however, that it comes in the form of exercise weights, and is very, very heavy.
Another large supply of lead items can be found in an unmarked Boxing Gym directly southeast of Pickman Gallery or directly behind Old North Church. Look for a green door.
An even larger supply can be found in the Federal Supply Cache 84NE.
Shipments of lead can be purchased from KL-E-0 in Goodneighbor, Tinker Tom in Railroad HQ, Cricket and Deb in Bunker Hill.
The Wreck of the FMS Northern Star, just below Warwick homestead has a total of 38 lead (1x 80lb barbell + 2x 20lb dumbbell) on the deck/top of the ship right outside the main hideout.
A huge amount of lead can be found at the Atom Cats Garage, next to the coolant pumps.
With the Scrapper perk lead can be obtained by scrapping armor modified with the lead lined mod.