Hide & Drink, leather thimble — Fits perfectly. I can even type with it after sliding down it over my first knuckle. When new, it's juuussssst a bit tight, which means that when it loosens up as it ages, it should still fit pretty good.
Clover leather thimble (レザー 指ぬき), size large (part number 56-815)[2][3] — It's very similar to the Hide & Drink thimble, with some important differences — The seam (the one in the anterior/posterior direction) has noticeably less bulk, the diameter is just slightly larger (which is perfect for me), and the leather feels softer.
Clover Mfg Ct, Ltd in Japan[2][3] is a decent-sized company with a long history, so hopefully its products will be available for a long time.