Warning! Just because one of the sources below is listed, it does not mean that everything at the store will work. Some shops have historical and fantasy stuff together.
If individual items are listed, those should good.
Note! WicSaga does not check materials, so long as it looks close enough. However, during warm events, we highly recommend linen, silk, or wool, as those breath better. Colder events often require warmer clothing, and wool can do that well, possibly cotton too.
https://raymonds-quiet-press.myshopify.com/ (Raymond's Quiet Press is also on Etsy)
https://www.der-roemer-shop.de/Home
https://www.kultofathena.com/culture/roman/
This Roman Tunic from Armstreet is made of linen, and can be custom made to size and color.
https://burgschneider.com/collections/burgschneider-ancestry
https://www.battlemerchant.com/en/topics/vikings-amp-normans/
https://www.kultofathena.com/culture/viking/
https://burgschneider.com/collections/kyivan-rus
Burgschneider has this Grey tunic as mostly wool with a mixture of other materials. They have this in other colors which may or may not be in stock.