Alright, basically you can find one on Amazon for just a little bit. I've used mine for programming with my TV, so if you're interested in programming, you might want to learn Python and Linux (for Linux, just audit each course individually to learn for free).
Though if you don't want to program it, you can just use it as a regular computer. I bought a kit for the Raspberry Pi 4B+ and it was really good, it contained everything I need (you pretty much need all the components in this kit except the case to run the Raspberry Pi safely).
Just be warned, this kit is over 100 dollars. Still, it can probably replace your current computer, and even be portable should you properly store it each time and get a portable monitor for it