This is a very simple tool that will output the status code that you send to it. Just make an HTTP GET call to https://maketools.net/http?status=xxx with xxx being the 3 digit status code you want in the response.
You can use the optional sleep query parameter and provide a value between 1 and 35 to delay the response if you wish.
Here's a complete example. You can click the following link to see how it works: https://maketools.net/http?status=200&sleep=1
This can come in handy when testing integrations to ensure your error-handling routes are set up correctly!
httpstat.us is probably a better option to be honest, but it was offline/overloaded a few times for me so I have created this simpler version as a backup :)