Not sure about the T5, don't know if any of the companies make one or even make bulbs that size for a DIY. As for the LEDs. You can always do a DIY of them.
As for a 24" fixture. Lots of copanies sell those. Some have LED moon lights. As far as LED DIY setup I know NanoTuners sells them but if you search the web you will find other plays that do.