Hmm, well a few things here.
1) We can not help you with where to download working versions.
2) Neo-Geo, like arcade roms are very picky. You must match up the right files with the correct versions.
3) it helps to download the bois files from the same set of the games.
If you just go searching for games and bioses, like most emulators, you could easily wind up whit a mess. I understand its not easy to find a full set but that is not our problem
If you still can get any where it may help to include more detail for us. I dont know any solution to help you base on what you gave us.