Adafruit has a nice selection of sensors and when there is some kind of communication required, a library to implement that. They also do application notes with circuit diagrams for cases when some electronic conditioning is required, however, they don’t have much of an industrial range of sensors and sometimes the better enclosure for a sensor is found in the industrial market.
Google searches are almost useless in some domains due to the heavy advertising SEO clutter, but you can get to what you want pretty quickly with an image search rather than web search. So if you’re looking for a temperature sensor encased in a metal probe with a waterproof penetration point and you type something rather specific like that into Google image search, you can probably see what you want. That’s the method I’ve used to locate sensor and other electronics devices.
If you type Pipe Temperature Sensor into Google images you’ll get a great page full of ideas. You can follow the image to the info page, and sometimes read a great blog post, or purchase what you want.