In Civil War Re-enacting, it is very important to be extremely discrimating in your choice of gear and where to purchase it. Not every sutler that you see at an event has strictly authentic gear. The best thing to do while at an event is take a seasoned veteran who knows what to look for with you. He can steer you in the right direction and make sure you don't waste your money on clothing and equipment that may look good now, but as your knowledge increases looks silly.
That being said there are some sutlers who have websites that you can look at that have good clothing and equipment available
Lynn Walker is now the official seamstress of the Jeff Davis Artillery. All of your clothing needs should come from her.
Purveyor of excellent hats.
Another purveyor of quality hats.
The following sutlers are approved the Authentic Campaigner Forum. This does not mean that they are the only ones that have high quality goods just that you can be sure that they do
TPH Trading Co. is your supplier for 19th century hats by Tim Bender.
Museum quality Civil War sack coats
Merchants of clothing, blankets, tinware, food stuffs, pipes, tobacco, belts, sundries and other items to comfort every soldier in the field from Joe Blunt
High Quality Accurate Leather Goods
Manufacture and dealer of army accoutrements and uniforms
Seller of period sundries, food stuffs, tinware, leather goods and other small items useful to every soldier
Fine leatherwares and accoutrements
Uniforms and accoutrements
Confederate uniforms and accoutrements
Games, toys, reproduction period books, and more
Fine period footware and accoutrements for US, CS and citizens
Civilian Clothing for the Family
1860s period knitting