Closest thing to natural sunlight i've used to grow bananas indoors was a 400 watt 6500K Metal Halide bulb with the best reflector on the market. My other hobby is reef aquariums where lights are a HUGE deal. Sunlight color is about 6700K i believe. The chlorophyll in the leaves respond best to certain EM frequencies and you'll have best chance of meeting those needs with a "daylight" bulb. If you want the cheapest setup, go to homedepot, buy a simple shoplight and 2x48" daylight (6500K) fluorescent bulbs. They are normal output bulbs, so the plant will need to be pretty close to the bulbs (within a foot).
Ideal setup, IMO, would be a 400watt metal halide Iwasaki 6500K bulb with pendant reflector hanging from ceiling. But this may be difficult in an office. Plant cannot get near the MH bulb or it will burn.
Another option is you don't mind spending a bit more it to buy a pendant lighting system made for aquariums. There are lots of options on bulbs that will put out a lot of light and in the correct spectrum. VHO, T5, MH, CF etc, all put out more light than regular fluorescents. Just make sure the color range is between 5000K and 7000K. Good online sources for pendants would be
Aquarium Lights Hellolights.com or
Aquarium Pet Fish Supplies, Tank Accessories, Products & Equipment.