Soul of the Warrior - Owned by the Centurio of Legio VI, this site will cover many of your clothing-based needs.
Caleb Burch - Can make practically any clothing based on custom measurements. One of the best historical tailors in the U.S.
Marled Mader - One of the best weavers and seamstresses in Europe. Can make tunics, cloaks, winterwear, or otherwise in hand-woven, hand-dyed fabric.
ECHO Historical Textile - Sells a variety of fine quality fabrics, woolen cloaks, and other historical garments in naturally dyed colors.
Kram Bu - One of the best weavers and seamstresses in Europe, sells a variety of reproductions of Iron age and Viking age garments, and can weave naturally dyed cloaks.
Elizabeth Da'Born Art and Textile - Again one of the best weavers and seamstresses in Europe. Can make a variety of reproductions of Iron age or Viking age garments.
Valeria Corvina - An excellent Italian seamstress specializing in Roman-era garments, she can make any historical garment you need.
Medievaldesign - Offers a complete first century panoply based on custom measurements. Sells a fringed sagum and a paludametum as well, and offers winterwear.
Fabrica Cacti - Based in Poland, they offer a variety of historical clothing including legwraps, cloaks, tunics, hats, and more.
Made in Duendecya - Can make historical Roman clothing in any authentic color. Based in Spain.
OldCraft Workshop - Sells a variety of fine quality woolen saga in various shades, both artificially and naturally dyed, and can make other historical garments too.
B. Black and Sons Fabrics - Offers a variety of 100% wool in different weights and twills.
Dorr Mill - Offers a variety of 100% wool in different weights and twills.
Woolsome - Sells a variety of 100% wool in different weights and twills in undyed, bleached, and modern dyes. Run by Legio XXI in Poland.
Fabric Store - Covers all of your 100% linen needs.
Linengraphy - Sells herringbone weave linen in a limited color selection. Based in Lithuania.