After accummulating a drawer full of thermometers, my advice is just spring for a Thermapen, which you cannot find on Massdrop (Lavatools is not the same). The Thermapen Classic dropped to $80 after the Pro was introduced, and the Classic is all you need, simpler and better, actually. You're going to end up spending that amount of money trying to save money avoiding a Thermapen. Just buy a Thermapen.
The time it takes to get a stable temperature reading is always given as a best case number. Triple or quadruple it for reality. Then decide if it's O.K. Do you really want to get the temperature of the fry oil 20 seconds ago?
This is from the New York Times-owned Sweet Home/Wirecutter review and recommendation website:
"The major technology difference between the Thermapen and its competitors has to do with its thermocouple sensor. The majority of instant-read thermometers (including the Javelin Pro Duo, our mid-level upgrade) use a thermistor, a small, relatively cheap-but-accurate resistor bundle stored in the tip of the probe. The Thermapen’s thermocouple has a thin sensor wire running down its whole probe, while keeping a more extensive set of reading and calibration electronics inside the sizable body. Because the wire has less mass than the thermistor nodule, it registers changes in temperature more quickly. That thin wire also allows for a thinner probe, helpful for thin fish filets and reducing the size of juice-releasing punctures."
The probe of the Thermapen is really thin compared to all the competitors.
It annoys me that nobody in the consumer market competes with these guys, but that is the way it is. How hard can it be to clone or even imporove on the Thermapen? It's a simple engineering project. J. Kenji Lopez-Alt at Serious Eats recommends the Thermapen as the "undisputed heavyweight champion of thermometers, but it has one major downside," the cost. Just pay it and be done with it.