You can find seeds and plants on eBay, though some of the seeds sold there are not fresh. You can buy plants at
Montoso Gardens Botanical Garden and Online Nursery (the owner of this Puerto Rico nursery has become a good friend of mine and is very reputatble). You can also buy seeds from a nursery owned by a guy I know in Hawaii at
TROPICAL FRUITS. You could also buy fresh berries from the site I linked above and plant those seeds after surprising some friends with the berries.
I paid about $200 for a large plant as small plants I had bought did nothing. However, I followed the advice of a friend who suggested I grow it in full sun in my greenhouse and I fried the leaves in just a few days and it's been struggling for six months to recover. I don't know if it will make it or not. This is the last shot I'm going to take growing this plant.
Good luck!!!