I'd pick up some from Greenlight Depot. They beat Lowes price on 8' HO lamps. I'm guessing your fixture has 4' lamps if there are 8 of them. If you don't have HO lamps, Lowes or Home Depot is probably you're best bet.
Make sure you get the frosted lenses/finish on the tubes.
And I'd go straight wire on the fixture, bypassing the ballast. The ones below work with or without a ballast. They are similarly priced to big box stores.
The LED tube and works with most T8 electronic ballasts. The advantage to this tube is its versatility. Not only can this tube work with a ballast, it can also work without a ballast, directly wired into AC100-277V. Great selection of LED Tubes for sale.
greenlightdepot.com
In at least 5000k color temp.