I just found out about these:
http://www.menards.com/main/p-2407785-c-7482.htm
The Sylvania/Osram is a 19 watt T8 LED bulb, but the best part is that it's a TRUE replacement! You do NOT have to modify the fluorescent fixture in any way! (It does have to be electronic ballast though, which all mine are…)
Very bright. The pair of bulbs that I got are 4100 Kelvin, but it's a much nicer color than anytime I've looked at a 4100K fluorescent tube. (Maybe there's less of a green spike to it?)