I actually have a 20 Gallon High that i just decommissioned. Let me know if you're still looking. It is in fantastic, like new condition.
20 gallon high metal stand
Coralife T5HO fixture with ZooMed FloraSun and UltraSun bulbs.
2 bags of Flourite black gravel in the tank
Fluval C3 filter
Still has the substrate in the tank. Took it apart 3 days ago. You can see it in action here: