If you have Menards in your area, I'm pretty sure they carry an American Fluorescent shop/industrial style fixture that's HO out of the box, probably with an electronic ballast. I don't know much about them, but I've seen them on the shelves. Some
Lithonia fixtures can be converted to HO without modification. All you need to do is flip the end plates around. Beware that other Lithonia fixtures appear to be narrower now, and might not have enough space between lampholders for any kind of T12.
I have several of those
Metalux fixtures. They are not HO-ready like the Lithonia, but are easily convertible to ordinary T12, and probably could be modified to accept RDC sockets without too much difficulty.