I believe that it is in fact the thermistor from the data sheet. However, I believe you can exceed the rating and get to 300 C, although I believe accuracy would suffer due to this.
If you really want thermistors that are accurate, reliable, and are rated for those sorts of temperatures, you unfortunately have to pay for it. But since you want to cheap out, I'd order however many the minimum order is from this fellow, and then test them against a good thermistor, or thermocouple to make sure you've got reasonable accuracy. If they work, all the way up to 300C, order your 500. But make sure to test them at 300C, or whatever your peak temperature is, for an extended period. Most things have safety margins designed in. Hopefully there's enough of one on these.
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