You may be able to find the sheet music in a music store. 'Viva la Vida' has the same melody as about eight other published songs, so you might be able to find the sheet music for one of those.
Your local music store.
Tomi Petteri Putaansuu
You can find choir sheet music for a variety of songs at music stores, online sheet music websites, and through music publishers.
You can find sheet music for piano songs by searching online music stores, websites dedicated to sheet music, or by visiting a local music store that sells sheet music.
You can find drumset sheet music for popular songs at music stores, online music retailers, or websites that specialize in sheet music for drums.
You can find guitar sheet music for popular songs at music stores, online music retailers, or websites that specialize in sheet music for guitar.
You can find jazz standards sheet music for popular songs at music stores, online sheet music websites, and libraries.
You can find a collection of songs for recorder sheet music at music stores, online music retailers, or websites that specialize in sheet music for various instruments.
You can find electric guitar sheet music for popular songs at music stores, online music retailers, or websites that specialize in sheet music for guitar.
Music Notes is a really good site to get original digital sheet music for songs at a reasonable price. It does cost, but you get the music instantly because it is a digital copy so you can print and use it straight away.
Check out this site. http://www.mycoldplay.com/home/2008/07/12/sheet-music-for-coldplays-violet-hill-and-viva-la-vida/ It has all of Coldplay's best songs in Pdf. form. It's Great! Or alternatively, instead of looking at a dead-end site, go here: http://www.abcmusic.net/download/free-sheet-music/265/coldplay/lost.aspx There's a small download button on the right side, but it has it. If you don't want to download it, then you'll need to look for another. The music itself is not perfectly like the acoustic version, but it's good enough that you can improvise it to.