Mahachanook Mango Trees in South Florida
Excalibur Fruit Trees in Lake Worth has the Mahachanook mango trees for sale. They have both 7 gallons and 25 gallons. I am not sure if the 25gs are for sale but the 7's are. The 7's were all recently potted up from 3's though so they haven't fully rooted out yet.
Here are some pics of the tags and the 25 gallons:
They were in quarantine for 2 years so according to that tag they came out of quarantine last year.