Any monitor, that can display standard PAL/NTSC signals (ie a TV set) can be used as a monitor.
Not all got antenna connection though. And many use connectors that the normal atarian isn't familiar with.
I suspect that you won't find anyone selling the cable you want, but if you look around on the net, you will probably not have any problem finding the pinouts of the monitor. The pinouts of the ST monitor out shouldn't be hard to find either.
Making your own cable from there shouldn't be hard at all.
