So it's not a search you want, it looks like a link to a particular category. So your description and title gave the indication you wanted a search, with no examples it was very difficult to decipher what you were indeed looking for. You're looking for information on Categories.
If you set up a good category structure, where posts can appear in more than one, you can set up navigation by just linking to those categories.
So if you had:
- North Face
You can include a post about North Face Harnesses in both Climbing Equip. > Harnesses and Brands > North Face.
This is how I believe a similar functionality could be achieved.
Then in WordPress you could see the list of items by going to:
You could add a + icon linked with one of the above URL's. This is more of a high level explanation of how to achieve this. If you are planning on building a shop, you would need to clearly map out the crossovers of products into multiple categories. Hope this helps.