I am considering building a levitation but need some guidance from anyone in the know. Specifically, I would like to know if anyone can recommend a particular linear actuator? I'm thinking 24"-36" stroke, and what kind of battery do you find delivers enough power to have a decent speed? I'm not set on using an actuator if someone has a better idea, but I feel like that would be the most efficient and more easily hidden apparatus. This would be used at a halftime performance for a local band that would like to include a levitation effect in their halftime show. So that should give you an idea of the limitations I'm faced with. I'm open to any and all ideas!

Most cheap electric linear actuators are slow and loud. Pneumatic is the way to go if you can.

There are two Gamolo levitations for sale on MagicAuction.com.
An actuator alone won't do it. They provide the lift but the side stress is handled by nested tubing.
18 inch rise is the norm. They are all relatively quiet.