If you want the edible type which are mostly seedless, you need to get what is called a Tissue Culture plant that can take a few years to produce, or a larger pup/baby banana plant which will be quicker, but this depends on your climate, and ability to overwinter where you live. There are sellers that sell them on Ebay, and other places on the net. This site is a good place to research the varieties, and also the wiki. If you just want an inedible ornamental type you can grow them from seed. Mark Davies seed on Ebay in the UK is good, I just had some germinate today from there. There are a few types that can take the cold, but germinating bananas from seed can be time consuming and difficult so patience is required, or you can acquire something like an ornamental Musa Basjoo pup that is sold in a lot of places, that is very cold hardy, and will come back each spring from the roots. It looks like you are in around a zone 8B climate so should have a few choices, but it also depends on how much cloud cover you get each year. The forum at this link below might be able to help you as there are a lot of people that might live close to you there, and maybe can tell you where to purchase them where you live.
Hardy Tropicals UK • View forum - Bananas and relatives (including Canna, Ginger, Heliconia etc)