Celia is right, and it can even be simpler than that. Almost any good hardware store will have line that is perfectly well suited for what you need. You can hunt online and read specs 'till the cows come home, or you can drive to the store right now (if you live in a decent-sized town) and come home with line that will do the job and hold up well for years. And if it holds up for just 5 years instead of 8 or 10 (or whatever a top-of-the-line rope material would last), what have you really lost, in terms of value? Not much.
Just a hint: When it comes to threading line through openings that are hardly any bigger than the line itself, if that’s what you end up doing, you’ll need to melt the cut ends of the line with special care. One trick is to tightly tape each location on the line where you will make cuts. Otherwise, once you make the cut, even the tiny bit of unraveling which occurs immediately results in a diameter that’s way too big, so that when you melt the ends you get a hard blob on the end of the line that won’t begin to thread through the holes in your boat’s rigging. Go ahead and melt the end of the line while it’s still wrapped in tape, confined to its original size. Another trick is to “smear and spin” the melted material so that a tapered point is created. Still another trick is to “cut” the line with heat while spinning the line on opposite sides of the heat source to twirl the melted material into a point. This takes a bit of practice to do well. Setting up a candle or even a propane torch with a low flame works well (for persnickity work, I’ll I’ll even use a low setting on a very small oxy-acetyline torch, but that’s not equipment most people have on hand).
And yes, when it comes to knots, you can just use any basic applicable knots. If you are worried about knots coming undone (they shouldn’t, if you pick the right knots for what you want to do), you can wrap the tag end onto the main line with fine wire or tape. Function instead of prettiness!