New ideas for you are one click away with IO Scout Keyword Finder.
Here is a simple example. Let's say you make furniture from wood. Or your friend does. Or you already worked with some manufacturers. Or you didn't, anyway. We know that furniture is often oversized and requires extra shipment and storage costs, so you decide to consider manufacturing something smaller.
Here is what you do:
go to Keyword Finder
put in a keyword, let it be wood or wooden
additionally, you can exclude some words from the results, for example, if you do not want to sell wooden tables anymore
Click Search and here we go! Few great ideas for products from wood of small sizes, each gets thousands of searches:
As a next step, click on any of these keywords and see what users get now when they do such a search: