Laser Harp Help?

Powering everything with a 9V battery will mean you'll be going through batteries every couple hours. A 9V is ~600mah, meaning it can provide 600ma for one hour, or 300 for two, etc. You'd be best off locating a 9V power supply and plugging it into the wall, but I can understand that if you're on the road with the harp that it would be handier powering it from a 9V.

With a 9V supply you can put a pair of lasers in series and four pairs in parallel.

It might also be worth a test to see if the lasers illuminate well enough at 3V; 2 AA batteries (~2000mah) would give you >8 hours powering all eight lasers and would be a lot cheaper than 9Vs. I suggest 3V because I don't think the 'shack stocks 3xAA holders.