Where to buy a new touch sensor (for Shutdown/Turn On) for my XBOX360 S ?

I'm sorry, but Microsoft doesn't sell these pieces. The only thing you could do is see if any site sells used Xbox 360 S or not working cheaply so you can use it as spare parts.

Self repair is not allowed to be discussed on the forums.

Here is the hardware i need the have:

So i took my xbox to another room on my house and still did the same thing, so I went to a friend's house and tried it there but it still turns off. to just make sure that you know all the details I might have not mentioned when the xbox turns off it does
the sound it always does when the sensor is touched. Also if it turns off when I touch the sensor it doesn't seem to work (The disc sensor does the same exact thing as the power sensor). I can only turn it on with my controller but it turns off again. The
xbox elite already is almost three years old since I bought it on 2015 so it isn't technically 'new'.

I know it's a bit of a clichéd response for a Microsoft product, but have you tried turning it off an turning it on again? and by this I mean pressing the power button on the console for > 5 seconds to force a complete shutdown.

Audio problems are typically caused by issues with the sensor and so forcing a shutdown and restarting usually clear the problem.