The 12" T-5 bulbs can be replaced with LED "tubes". I have looked into it and the cheapest I can find them is about $30 per "tube". That's not in my budget so I haven't bought them. These will snap right into your fixtures but you will have to rewire the fixture. I'm not aware of anything that doesn't require rewiring.
The color is given as a temperature in degrees kelvin. What you want is around 2700 to 3200. That will look similar to an incandescent. The higher numbers (4,000 and 5,000) will look more blue and are not at all what I like for lighting.
