Simon,
I think Mimosa nursery in Anaheim might have a 15-gallon tree for $150. I bought some other citrus variety 2 wks ago and the guy there, Mike, said these 15-gal trees are going to be moved up in size now, so I got a good deal. The trees he said are over 10yrs old. So, I bought 2 trees, maybe 2" diameter trunk.
I know my local Home Depot (Brea) is currently selling citrus trees in 3-gallon pots for $35 each. The tree itself looks to be the same trunk diameter as the ones I bought at Costco last fall for $39 each in 5-gallon pots. These trees have trunk diameter or 1/2"-3/4" depending on what variety you buy. The largest trunk size will be the pomelo or orange trees. No Meiwa at Home Depot.
You can call Mimosa nursery to see if they have it. They don't let you go into their closed off screen room/greenhouse to protect against ACP. If they have it, and you want the big ones ($150) then I can hold it for you until you come up here to Fullerton.