I took a close look at the FastTrack railer that Sinclair posted.
See the end of the device, with the wedges built in, which put the wheels on the track? Well, the HO re-railer had a piece exactly like that, made out of plastic, built into the track, on each end of a straight track section. They were positioned in opposite directions, so that the car would be re-railed no matter which side of the section the car came in on.
I see no reason why I couldn't buy two of the Fast Track railers, cut them in half, take the two half sections that have the wedge configuration, gently bend them flat, and then just install one on each end of a 10 inch section. From what I can see, these sections already have slots cut in them, so that they will sit down right into the track itself.
If I undertake this, I will certainly keep you posted and put up pictures. Manufacturers are crazy not to sell this for O gauge. You can put a car right onto the rails, while looking straight down on the top of the car, without even tilting your head.