I hate that you haven't gotten an answer, so I'll give it a try. I really am not experienced with growing Trees in containers. Some thoughts would be dwarf citrus, dwarf crape myrtles (might be too messy on a deck), Little Gem magnolia. Possibly a large shrub which can also be considered a tree, like camellia (but might be too sunny for that) or tea olive. Some palms are winter hardy but I don't know which ones. Your best bet might be to contact your local nurseryman (not the big box garden centers) for ideas.
Laurie (lived most of my life in 9b)

Thank you so much, Laurie. I was just hoping I would find someone who could give me an actual success story. :-]

I do like the idea of the magnolia. I thought the same thing about the crepe myrtle - too much mess. I'll make the rounds of the nurseries and see if they have any suggestions.

I had a little gem magnolia tree in a 24" clay pot just off the side of a low deck for years. It did great. Decided to plant it in the ground so that it would get bigger. It stayed about 8' tall in the pot.

Try the Florida Gardening forum. Tons of people in Zone 9b and lots of traffic on the forum.