Hm, you might be in luck. According to VGC, I own the PS3 version of XIII but the 360 version of XIII-2...
I don't own a PS3 either.
I'm trying to see if my former roommate (who has a PS3) has my copy of XIII (so I know I'm not imagining it). If so, I'll be happy to trade my 360 XIII-2 for the PS3 version. It's from Gamefly, so the packaging itself is pristine. The disc itself has been used but looks ok to me.
I intend to get a PS3 eventually, so I don't mind having two games that I can't play for the time being (to add with the others).