It is always an option to use a solid color waist band like you see in Mike's pic above. Regimental kilts are always made with a green waist band. I've seen a lot of solid black used in kilts that are rather long, as you describe, and also kilts that have been altered (if you let out a kilt, the waistband it came with may no longer be long enough, so it gets replaced with a solid black).

Matt