Players can extract Ender Eyes from Portal Frames for Peaceful Victory

By Right Clicking on a filled End Portal Frame, an Eye of Ender pops off and the block becomes empty.

With this suggestion, players in Peaceful Mode have a non-renewable source of Ender Eyes, an average of 1.2 of them per Stronghold.

Playing with a random seed, one would need to loot an average of 10 Strongholds to have enough Ender Eyes to open one End Portal.

Since each Minecraft world contains at least 128 Strongholds, the odds of there being enough filled End Portal Frames in the world to open at least one of those Stronghold's End Portals is very very close to 100%.

If the End Portal stays open even if it's eye is removed, the first twelve Ender Eyes which the player finds can be reused to open as many End Portals as he chooses to.

After that, he can use the Eyes of Ender one last time to craft a limited number of Ender Chests.

To make finding those Strongholds less hard on the player, Master Cartographers could sell a Stronghold Explorer's Map for emeralds and a compass, or for emeralds and a new compass-like item found in Nether Fortress Loot Chests.