Work without any patch so I didn't need to look for one
You only need to config the save type, sometimes it's not available on VBA so you need other emus like BoytcottAdvance or RascalBoy Advance. Well, that's not the case of Boktai 2 because of the built-in light sensor, but this method works with SMA4, Mario Vs Donkey Kong or DBZ Legacy of Gokuu