The only place I can find with seeds in stock is
Rich Farm Garden with a packet of 5 seeds for $6.50.
Trade Winds Fruit has a packet of 8 seeds for $3.00, but they are currently out of stock. If you are not in any hurry, signing up for their "back in stock notification" might be useful.
You could also keep an eye on Etsy and eBay to see if seeds show up there. The only other site I found was selling 1yo
trees for $210 per plant, which seems just a tad overpriced.