Depends on what you're looking for. For uniforms, MOLLE equipment, stuff to that effect, you can look for military surplus stores, on online at websites such as Cheaper Than Dirt, US Cavalry, etc.
Stuff like vehicles, you'd have to look at the GSA auctions.
One can purchase army and navy surplus goods in the US on the official website for the Army. They will allow you to purchase the surplus goods for a price.
Army surplus
There are many types of products that can be bought at an army surplus store. Some of the things you can buy at an army surplus store are clothes, cabinets, knives, kits, gloves and many more.
you can purchase those clothes at an army surplus store. there is one located in abilene Texas. they also have an eBay store. there store name is actually army surplus. go check them out
"A cadet heater can be purchased at any hardware store like Home Depot or at a army surplus store. Usually they are for army recruits, but these days anyone can buy them."
army surplus
Best advice would be to check and inquire at your local military surplus stores.
The only place to buy an original M65 jacket would be on eBay or at a store that specializes in vintage army memorabilia. Newer styles of the M65 jacket can be bought at Army surplus stores.
c&c army surplus
army surplus stores
Official US Army clothing can be obtained through various channels. One option is to visit an Army base or post exchange (PX) store. Additionally, the Army and Air Force Exchange Service (AAFES) operates an online store where official Army clothing can be purchased. Another option is to visit a military surplus store, where authentic Army clothing may be available.
Some army knives can be purchased through some army surplus stores throughout the United States. They are also available through sites such as ebay and craigslist through private sellers.
There are many places to buy BDUs. Some include military surplus stores in your area, airsoft or paintball stores, or military surplus stores online. For example: Evike.com .Airsplat.com .bdu.com