Aren't they only available through Japan events?
I'm gonna answer this myself:
From Serebii:
The official site has updated and has revealed that during the World Hobby Fairy 2014 Winter, which is to be held later this month on January 19th in Nagoya, Tokyo, Osaka and Fukuoka, there will be distributions of various O Powers. These O Powers are O Power MAX and run for 60 minutes as opposed to the usual 3. The Powers are as follows: EXP Point Power MAX, Bargain Power MAX, Prize Money Power MAX and Capture Power MAX.
So MAX O-Powers are special O-Powers that are given out in Japan at distribution events. They're the same as regular O-Powers, except that they run longer.
Do you mean the highest-levelled O-Powers? If so, the highest O-Power level is 3. To get a higher level, you need to continue using that O-Power. The more of that O-Power you use, the higher level it will gain. The more usage, the more reward! :D
Hope I helped. :) Source