Chamaedorea microspadix is probably your best bet if you are in a zone 9a. They are pretty cold tolerant and when older surviving temperatures into the teens. They are very tropical looking palms (probably the most cold tolerant "tropical looking" palm you can find), eventually growing a nice ringed trunk, but very slowly.

Chamaedorea is definitely the best family of palms to look into if you want a thin trunk.

Good luck!
-Alex

Are you looking at growing in a pot or in the ground? You have more choice if it's in a pot as you can move it any time the weather isn't suitable.

I'd agree, Chamaedorea are probably your best bet. C. seifrizii is another good clumping one, often called Bamboo Palm. It's the most cold tolerant of the "bamboo" type Chamaedoreas and can take a bit of sun once they get a bit larger.

You could also try Linospadix monostachya or L. minor. They're single stemmed and slow growers. But they like high humidity and don't like direct sun.