Google has a nice feature that will only show you results from a specific URL. Put in in your normal search and follow it up with site:http://www.yoururlhere.com .
For your example copy in “best tip up option site:https://www.in-depthoutdoors.com” , and you will get a few good pages of results from just IDO’s site.
I find this is a good feature even for site’s that do have a search feature (which this site does have). It allows you to leverage google’s search and indexing strength, which I find is better for both the content of your search and finding older archived posts. A lot of site’s built in search seem to have a recency bias towards the latest posts.