750 c temperature sensor needed for jetpack engine

I am developing a jetpack, building and testing the ramjet engines that reach temperatures of 750c and I am looking for a great “High-Temperature Sensor” that will be able to operate at that temperature consistently. I want a hard-wired sensor so I can place them inside the combustion chamber, at the exhaust tail, on the fuel lines, on the fuel bladder and on the outside of the jet engine casing as well as on my feet. I want to be able to monitor temperatures during the development and prototyping of the jetpack as well as during flight. One option to increase the power output of the ramjet is to preheat the fuel. However, there is a danger of setting the whole thing on fire if it gets too hot. The temperature sensors can help make the jetpack safe and more efficient.
Please let me know if you have any suggestions for a sensor that could plug into the Uno.
Also I am looking for any sketch that is already set up to run a 12vdc fuel pump or running a ramjet, rocket or turbine jet engine. Thanks.

Thermocouples work at high temperatures.
How do you know that the upper limit is going to be 750c ?
Will the sensors be working in an oxidising environment?

Thermocouples are the only type I can think of that MAY work at that temperature. You'll have to look carefully for types that can handle your temperatures, as many may simply melt. The chemical environment is also important of course. You don't want to burn your sensor in the process.

750C feels low for a rocket exhaust, but I may be wrong. I'm not a rocket scientist. Normal flames, even candle flames, easily surpass those temperatures.