I don’t have a brand I would recommend, but I can say making your own extracts is extremely easy. Roughly chopping hazelnuts, toasting them, and adding them to a neutral vodka or glycerin would take maybe ten minutes and no special equipment. I went through an extract phase a while back and still have several, including a truly kickass coffee vodka.

Making it yourself isn’t fast, but I share your dislike of how hard it is to find unsweetened, reasonably priced extracts. I don’t want syrups, I like being able to control sugar content separate from additional flavors.

I do wonder how it would taste in comparison. I’ve never tasted hazelnut extract vs flavored coffee, creamer, or syrup, only ever in baked goods.

Torani is my go-to. Though I prefer different flavors to hazelnut so I don't know how theirs compares to others.

If you also like creamer, my ex is a huge fan of Coffeemate Hazelnut.

But I really like the other persons idea of frangelico or amaretto. I occasionally add some Irish whiskey and those other options would be tasty alternatives