One of my favorite shops in Paris is the always inspiring Merci, a collection of men and women's boutiques (very pricey) and home goods (well curated and a bit more affordable). They have a particularly wonderful collection of 100% linen sheets, towels, napkins, and bags in a rainbow of colors. I've been using linen napkins from here for years and they've held their color and shape well. The most basic napkins, at €4/apiece, aren't for sale on the website, but they're in store. I also really like these napkins which are online - they're cafe chic, with a red stripe running down the side.