In the Wild-Area outside of the Bar, there is a building right next to the train tracks that emits a dangerous amount of radiation. Next to it there will be a small white tower. Climb the ladder to the top of that tower and jump up onto the hand. Get a small running start and leap to the roof of the radioactive building.
You will see holes in the roof. The one you want has several boards sticking out of it. Don't run right into the hole, as there is a very deep pit below it with an electrical anomaly inside the pit. If you fall into the pit you will have to reload from your last save, so make sure you save your game on the roof before you attempt to drop in.
Once you navigate through the boards and use them to carefully get into the building without falling into the pit, search the rooms for a large safe. There are only about 5 rooms in the building so it shouldn't take you long to find it. Inside the safe is an armor plated anti-radiation suit. It is worth 30,000 RU and protects much better than the STALKER suits.
Put the suit on immediately as you will have received a nice amount of radiation at this point. Bring a few scientific med kits, or a few needles with you...you'll need them, or at least one of them. Ensure that you will be able to carry an extra 5kg so you can take your old suit back to a trader to sell it. STALKER suits get about 9,500 RU in trade value so it would be wise to take it with you.
There is only one way out of the building. Having the suit on should protect you for a good amount of time, so speed isn't an issue at this point. Find the room with a broken window. Move one of the crates in that room beneath the window. Hop up and use the "low crouch" (default ctrl+shift) to get out the window.
Now you have one of the best suits of armor in the game