I've done a ton of ballast replacements. If you already have 4' T-8 lamps, get these, or something similar:
GE 120-Volt Electronic Ballast for 4 ft. 2-Lamp T8 Fixture-GE232-120RESDIYB - The Home Depot
If you wanted 4' T-8 LED-replacement bulbs down the road, this electronic ballast should...