Where can I download karaoke tunes

[LuisV]

No clue if this is in the right forum, please move it if I'm violating any rules.

My grandfather and grandmother are celebrating their 50'th anniversary and we have to sing a song. We wrote our own lyrics and wanna sing it on the tunes of "yellow submarine" by The Beatles. Now we just need to find just the instrumental version without vocals, anybody know where I could find this? Thank you!