I really like Grunwald, a Danish webstore I found through one of Voxsartoria’s posts at StyleForum. Run by one Mr. Torsten Grunwald, the site is dedicated to providing men with the finest made accessories from around the world. That includes:
Made-to-order handkerchiefs. The white linen is sourced from Italy and each handkerchief can be sized to order and cut with a specific border design. Perhaps more interestingly, they can also be custom embroidered with your monogram, though of course you should never let those initials show when the hankie is in your pocket.
Voile and chambray shirtings. Woven on old looms in France by Simonnot Godard, such shirtings can be difficult to find. I recently picked up some blue chambray at A Suitable Wardrobe, but other than that, I only know of a couple shirtmakers who carry these. Very nice if you have shirts custom made.
Antonio Muro neckties. I had the pleasure of trying on a few of these when I was last in Naples. Though E. Marinella and E&G Cappelli get talked about most when it comes to Neapolitan neckwear, Muro ties are certainly nice as well. They also feature slightly bolder designs than what you’d get at Marinella or Cappelli - less English repp stripe/ Macclesfield geometries; more 1930s Naples.
Other things worth mentioning include Begg scarves, Mazzoleni peccary gloves with mother of pearl button enclosures, and some of the nicest Francesco Maglia umbrellas I’ve seen around. Nicest, I say, because of the conservative canopy, dark maple wood, and slightly shaved shaft (which will give a slimmer profile when the umbrella is furled). Prices here are expensive, but actually a bit cheaper than you’d find elsewhere (for example, I believe most Maglia umbrellas outside of Italy sell for above $300). Browse their site when you have a chance, and subscribe to their blog. Torsten maintained a Danish only site for a while, but now some selections have been translated into English.
(images below from Grunwald and Journal of Style)