I can't find it anywhere and I want to know if someone has it.

Sorry for the terribly late reply. I came upon this thread while I, too, was looking for, well, not the song, but more info about it.

I don't believe there is any official release of this track or any other songs related to this game yet. (Keep in mind that the game is still in location testing in conventions and Japanese arcades. It's likely the OST will be released around the same time as the game, which is pegged to be released sometime into the next year, apparently. For now, I suggest going to a site like keepvid.com and downloading the .mp3 of it from the Youtube URL for the time being. Perhaps once the game is released, you can catch it on this site. Nearly everyone I know loves the music from G.G. games, so it without a doubt will end up on here after an official release.

cloud-vibe.com/audio/208592225/278235240/Daisuke_Ishiwatari_amp_Naoki_Hashimoto_-_Heavy_Day_Guilty_Gear_Xrd_-SIGN-_(cloud-vibe.com).mp3?dl=1

Have at thee, lovers of rock.