CMs have access to certain exclusive pins, yes. pretty much every arm affiliated with the theme parks/studios has its own pins available to all cast members. CMs can trade these pins with the public if they wish, but they're not allowed to re-sell them.
WDI is a popular source of such pins for example (they have a shop on site called Mickey's of Glendale). They often even make pins available for sale through the hub/CM portal. I have a few from there although I'm not a huge pin collector.
I also have a pin from Walt Disney Studios which is marked as being from the Disney Employee Center.
and this not to be confused with other types of cast member pins (or hidden mickey pins nowadays) which are special pins released by Disney only through cast members, so they were never available for purchase.