While these are plastic, they are exact "look-alikes" for the factory grips:
http://www.vintagegungrips.net/ao-c77.html
There are a fake Colt "type" grip available on Ebay, but these are crappy, and to any real Colt "person" look like crap.
These are foreign made grips. Note the odd S&W-like checkering. The shape is wrong too./
These are often sold as real Colt factory....... they AIN'T.
Same grip only without the medallions and made of a hardwood. At one time CDNN sold these for as little as $9.95:
Here's the RIGHT genuine factory grips for the 357.
The early fully checkered version.....EXPENSIVE when you can find them:
The Second Type factory grip....... Still expensive.
The Colt 357 model would have come from the factory with SILVER Colt medallions.
In that era, only the Python had Gold medallions.