choosing a song and finding the instrumental

[JesA]

i'm entering my school's talent show in April, and ive already narrowed my song choice to 5 songs...of course, im gonna sing....and i need help choosing a song...these are my top five...

• Norah Jones - Don't Know Why
• Corinne Bailey Rae - Like a Star
• Nina Simone - Feelin Good
• Green Day - Boulevard of Broken Dreams
• Bread - IF

and then, if i finally choose one, how do i go about finding an instrumental track to sing with in the actual show? I've always wondered how people singing in a talent show find the instrumental track for their performance....i'll do whichever song i can perfect and find an instrumental for...that prolly knocks out the two oldest songs, Feelin Good and IF, cuz it would be hard to find an instrumental to songs that are 40-30 years old....

so can anyone help?