One advantage of fluorescent bulbs is that they last very long and therefore are cost efficient. The brightness of a light bulb is measured in lumen, which in this case is 270 lumen.
From Amazon
L6/20 9 6W 4000K
LED Bulbs
Osram T5 Fluorescent Tube 6W 225mm 9 Inch Cool White - 008899
Big on Electricals
Osram T5 Fluorescent Tube 6W 225mm 9 Inch Cool White - 008899