Call of Duty Apparel
Call of Duty has been around enough to amass a large amount of clothing options. There are tons of t-shirts, hoodies, jackets, etc. to choose from for a big Call of Duty fan. A good place to start would be the Call of Duty shop itself which has plenty of apparel to choose from at prices that don’t seem too unreasonable. Also jewelry such as dog tags and bullet pendants are a good accessory to keep an eye out for.
Your next best bet would be searching something like Amazon or eBay. Both have a ton of Call of Duty apparel listed on there. If you want a whole outfit though, might I suggest Ghost’s threads from Modern Warfare 2? This site has a complete outfit that you can purchase which is pretty sweet especially if you’re into cosplay.