Circle (2 Pack) PL-13W 827, 2 Pin GX23, 13 Watt Single U-Shaped Twin Tube, Compact Fluorescent Light Bulb, Replaces Philips PLS13W27 GX23 and Sylvania CF13DS827 GX23 - Amazon.com
Feit Electric 13-Watt Equivalent PL CFLNI Twin Tube 2-Pin GX23 Base Compact Fluorescent CFL Light Bulb, Cool White 4100K (1-Bulb) BPPL13/41/HDRP - The Home Depot