A year and a half ago, I was on the exact same quest for the green O scale BCR caboose. I contacted Kelly's Kaboose and they told me at the time this one was very rare and they didn't have it. But they had the red, white and blue version from K-Line so I bought it.
Shortly after, still hunting for the green caboose, found one from Atlas in O scale on eBay and bought it too.
The K-Line caboose has more details than the Atlas one but I like them both.
Good luck in your search, I'm sure you will find it one day.