I don't recall ever having seen saguaros for sale. I suggest getting a Peruvian old man cactus. I've had one for over 50 years and wouldn't trade it for anything.
They grow in Arizona.
They grow very-very-slow.
I am obsessed with cactus and have a couple around my house I was looking into getting some more and was wondering where I could find a mini saguaro cactus that I can fit in a pot