Puchase from vendor
A couple vendors sell the Maximilian armor after prerequisites are met. After you complete the Great Crystal adventure story line in Giruvegan you will receive the Treaty Blade, after which the Maximilian armor will be unlocked and available at the Necrohol of Nabudis Shop from the Baknamy Merchant for 17,000 gil. The second vendor is Lok of the Phon Coast Hunt Club, who will sell you the Maximilian armor for 25,500 gil after you give him 30 trophies.
Find in treasure chests
There are two treasure chests that have a small chance of containing the Maximilian armor. The first chest is in the far southeast corner of Site 6 of the Llusu Mines that has a rare chance at spawning the armor, and the second chest, which also has a small chance of containing the armor, is in the upper part of the Giruvegan Crystal Grande dungeon in the Sirhru Phulaam Praa'vaa.
Rare drop from Elvoret
Elvoret is a gargoyle located in Necrohol of Nabudis. When defeating Elvoret you have a 5 percent chance of being able to loot the Maximilian armor from his dead body.
Extra Sets of Armor
Because there are multiple ways of acquiring the armor it is possible to receive more than one set of Maximilian armor. Extra sets of armor can be sold back to a vendor for a good amount of gil.