SUNLITE 13W 21 inch Cool White 4100K Fluorescent Tube Bulb - F13T5/CW - Walmart.com
4 Pack of 8W/21" T5 LED Tubes Replace 13W Fluorescent Tube for Undercabinet Lights Directly to get Over 50% Energy Saving and 50K Hours Life - Amazon.com
F13T5CW – T5 21 Inch Under Counter Fluorescent Bulbs Cool White 4100K 13-Watt F13T5/CW 21” CW Long Life Replacement Tubes for Under Cabinet Lights – Pack of 6 Bulbs - Amazon.com
Bluex Bulbs 4 Pack T5 21 Inch LED F13T5CW LED Replacement Bulb F13T5 LED 9 Watts 920 Lumens Cool White 4100k F13 T5 13 Watt Bulb - Amazon.com