I'm curious about this as well. Does your employer know that you sold or not?
I'm curious if anyone has done it without by using a private contract between buyer/seller (google: forward contracts).
It means they have to match the offer or let you sell. It’s exactly like a national best bid guarantee in a real market.
If you can find a buyer for a certain amount, you can sell for that amount. The company can just opt to be the buyer.