Never collected them myself. But I'm pretty sure if you go to the right spot and right time, you can find some.
However, this kind of information is usually considered "secret" because of:
1. Money (more supplier, the price will drop)
2. Protect the species (so people from all over the world wont swarm)
Megasoma punctulatus was considered rare for a very long time. but do you know if you go to the right place at right time, you can find 50~100 a day?