I love looking around for this type of information
Dracaena 'Janet Craig Compact'- this has the same water and sun requirements as the dragon
tree and also is a slow grower with a maximum height of 4 feet. It looks like it might be a good choice.
New Zealand Flax - I love the color of this one. It also matches the sun and water requirements of the dragon
tree. It's maximum height is 9 feet.
Spanish Bayonet - This type of yucca maybe an option depending on the size of pot you have for your
plant. They do get wide. It also matches the sun and water requirements of the dragon
tree.
I hope something here helps you get an idea of what you may want.