I'm in a small niche but there are still things that no one sells. I see these things mentioned in books and forums on my topic. Those are the things I focus on to make or sell, and having this oddball stuff is what distinguishes my shop from all the others in my niche. I don't make a ton of money because there is only a small market for these things, but I'm still here ten years later, no evil eye. The oddball stuff is what I can charge the most for, since there is no competition. It does require a body of knowledge and persistent sourcing of materials. Not sure if that suits what you are doing.
We asked several of our suppliers to add an innovative niche product to their lines. It wasn't something one could sell enough of to build a site for or make a living from. But we were confident there was a good market for it. Still, no supplier ever put the product into production.
We finally decided to pony up lots of cash and have it made specially for us. We had to order far in advance and buy a lot at a time. We were taking some risk. The maker was taking none.
But it sold great. We reordered often and we alone sold it and at a larger markup than usual for 18 months...
... Until the manufacturer looked at the volume we did and put it into his regular line available to all (and at slightly lower price than we paid).