There are a ton of off brand styluses, but I don't know if they have the same features that the pencil does or not. You could always buy one of them to see if you like the iPad for drawing - just read the reviews first to make sure you don't get a shit one.
My iPad is too old for the pencil so I got a cheap stylus and it's fine. I don't use procreate much because I have the art skills of a kindergartener and I keep forgetting to practice, but it's pretty slick.
My advice would be to buy a used iPad a generation or two old if you only want to draw on it. You aren't buying it for its features, so one that's a couple years old should work just fine for you. It'll be cheaper, but I don't know by how much. Apple products keep their value surprisingly well, but I'd say you'd likely save a couple hundred bucks at least. That would pay for the pencil!