Change field-order flag in MPEG-2 program stream?

[Trixter]

I have hundreds of MPEG-2 program stream files where, for reasons unknown, the field order flag in the program stream is wrong. This obviously leads to incorrect decoding on software players, showing the fields out of order which results in jittery playback.

Is there a utility or batch process I can use to simply set the field order flag in an MPEG-2 program stream to a specific field order? Linux or Windows is preferred. The goal is to avoid anything interactive, since I'm not going to do hundreds of these interactively.

I'd like to do this without demuxing/remuxing because I'm worried about sync. I have FFMPEG installed, but wasn't able to figure out how to do it with FFMPEG without remuxing.