In the 19th century, there was a market for orchestral reductions to be played at the piano. These days, there is less demand for this sort of thing and the old ones are largely out of print. There is still a demand for reductions of concerti and vocal music (for rehearsing, for example) and, generally, the same publisher who publishes the full score will have piano reductions if any are available.

In an emergency, I would play from the full score, though that certainly requires skill. If you have need of scores that are not available, you will probably want to investigate music transcription software and MIDI instruments. I can not recommend anything specifically, because I do not prepare my own reductions.