I don't know exactly what you mean by 'back-up copy', but if you're talking about where you can get another copy of MK2 for the PSX, try eBay.

what i mean is a copied version

well your probably only saying "back up copy" because you don't want to get busted for not having the game and wanting to download it for free

Do you already have a copy of MK2 for the PSX?

nope

Oh... so what exactly are you asking for? Is it the game, or do you want someone that's on the board to burn you a copy of it or something?

I think I shouldn't have closed this yet, but ah well. I've heard that the PSX version is not an official release, I've heard it is, so I don't know. ebay has no records of it, so wether it's an official release or not isn't clear to me. If it was an official release, then you cannot ask about obtaining it illegally, we don't allow that. It might be a different story if it was some kind of a hack, but it's still Midway's characters and game, so it's still edgy.
If you're gonna try and obtain it illegally, don't do it by asking for it on this site.