There's a brief fireworks scene in the tutorial. You can find all kinds of firework clips, still and animated on various web sites... if you're willing to pay fee which can get expensive. Do a search on stock video footage or something similar. I found the two belown in 30 seconds.

http://fireworksland.com/html/pyrovideo.html

or a a freebie that asks for credits.

http://www.camcorderinfo.com/stock/NY_FireWorks.htm