If you don’t have any device that already come with a pen that can run Windows (like a 2-in-1 laptop), you probably need a whole new device, not just a pen. Search for “graphics tablet”. The most notable brands are Wacom, Huion and XP-Pen (personally my trust to them is roughly in that order). You can get some incredibly cheap (and good quality) ones nowadays, if you choose one with limited functionality and no display. Then you connect it to your PC, and draw on the black surface while looking at your normal monitor. It takes some adjusting and it’s not perfect, but it is very cheap entry to digital painting.
Here is some topic on the forum with plenty of information, though it’s a bit messy, but you can search it for models you think you want to buy: A community curated list of working tablets with krita!