Some ingredients can vary significantly depending on the brand used.  I don't endorse any particular product, but naturally my recipes are designed to work with the ingredients I have on hand. 

Bezegaard agave syrup is sold by a Belgian company.

Almond flour
De Zuidmolen is a mill in the Netherlands which I order almond flour from directly, as it is much cheaper than the small quantities which can be found in health food shops.  This product is not suitable for gluten-free cooking because it is ground in an environment where wheat is present, but it is fine for low-carb cooking.  It has a slightly crumbly texture, which means that there are visible small lumps in batter when I use it, but this isn't obvious in the crumb of the finished product.

Coconut flour
Noble House (Aman Prana) coconut flour is distributed by a Belgian company.  It is a Fair Trade product from Thailand.

Originally I used Now stevia extract (from an American company).  Later, I used Paraguaya, which is imported to the Netherlands and produced in Paraguay.  This product is more diluated; in a recipe which used 55 drops of Now, I had to use 65 drops of Paraguaya to achieve the same result.  Now is described as a stevia extract in a base of water and 11% alcohol, while Paraguaya lists the following ingredients: distilled water and stevia extract.

Sosa Fresh is a brand from Spain.  This is what I used in my earlier recipes, but when I ran out, I switched to Xlear's Xylo Sweet, which has a more granulated texture, without noticing any difference in the result.