You know, I think it has to come down to trial and error at this point... There are TONS of type K thermocouples available at ridiculously low prices, it's things like the temperature range, resistance to moisture, high temperature leads etc that make the difference in price.
Regardless, you want to get one with the mini thermocouple flat blade type connectors, or plan on buying that connector separate, which is never really a winning deal because shipping for one connector will kill the bottom line price.
I bought two thermocouples to start out....
First one is a long needle probe from Thermoworks that is completely moisture and steam proof and can handle over 2000F on the probe. The negative is it was maybe $36? IDK, expensive for a probe... Also, though the cable is completely water/steam proof, it's temperature rating is rather low, so the cable needs to remain outside of the pit.
Second one was a very cheap type K pit probe sort of thing, short thick unit that you would poke through a hood like the hood thermometer. The thing I paid most attention to when selecting the cheap probe was whether it was an isolated or grounded type probe. There had been lots of reports of thermocouples acting strange when touching the grill, or when you touch them while barefoot etc... Problems that seem to occur with grounded type thermocouples. I have always used isolated type thermocouples and have never had any issues so I stick with that. In each case, both Thermoworks and the Amazon seller, I had to ask the question "Isolated or Grounded?"... TW's was quick to answer and so was one Amazon retailer, I bought one from each.
They both kinda work the same, perfect.
The Amazon one did have loose screws on the connector which was puzzling until I opened it up and tightened them, it worked just fine after that......
The thermoworks probe has been my work horse... From the day I plugged it in it has been outside in the weather.... So far through summer, a rough winter, spring and now summer again outside unprotected and NEVER missed a beat. The probe is a long thin bendable needle, so I can stick it in the top vent, or in at grill level and it doesn't interfere with the lid closing/sealing. I have had my "fauxmado" over 900F and it was no problem for this probe, even a huge temperature blume wouldn't top the 2000F limit. I am actively trying to kill this probe! LOL I have bent it this way and that, still going strong....
Mainly due to the fact that I like the thermoworks probe so much and I can't seem to kill it I haven't really been able to put the cheapo probe through the paces yet....