You want to check with a nursery that can buy from Zill's HPP. Sometimes they have 15 gal trees for sale, but I haven't been up there in a couple of years.
For a while during the late 2000's and early 2010's, there was a surplus of these, and fruiting jabo trees were going for under $100 on the wholesale market. Then someone came and bought everyone out. Prices skyrocketed and availability bombed.