There are lots of book CD combinations where the tracks have been rerecorded with only druss bass keyboard as appropriate. Alesis' used to make the PlayMate guitar trainer you put any ordinary CD in it and then could slow it down, change pitch and I thought it could reduce centre-mixed guitars but it appears discontinued and now there's a Playmate Vocal Remover instead.
Do start singing though you'll find it will improve your playing of some songs where the lyrics and strums work together. Don't worry about how you sound, choose a Bob Bylan song and you probably sound better than his Bobness already!