Advanced radiation suit (Fallout 3)

The Advanced Radiation Suit is a suit specially designed to stop radiation better than the standard Radiation Suit.

Locations
It can be found deep within Vault 87, in the Test Labs. When you get to the room with the Lab Technician's terminal (on a desk to the right) one of the options will be to unlock the storage room. Choose that option, then turn around and go back out the door you entered and turn left. That door is the storage room and contains the Advanced Radiation Suit.

Can also be bought from Moira at Craterside Supply (RARE and RANDOM spawn in her purchasable inventory) and Gustavo from Tenpenny Tower.