There are a few ranked Hard diffs that can give a 1000 combo. Some off the top of my head: Kuraki Mai's Winter Bells, Kowarekake no Orgol (SiRiRu's Pleasant diff), and Lee Jung Hyun - Welcome To My Style. The thing is that most of them don't give much in the way of leeway because they're not much over 1000 (they're quite good for the 750 combo... a lot more leeway than a map that's just over 750). Going to approved maps you can get a lot more leeway... Parapara Max will give you many chances for 1000 if you screw up.