Rolex has clamped down on spare parts. If two ADs both said this was a trade-in-only part then it's unlikely a dealer will risk selling a part outright without a trade-in.
If you're okay enough with the damage to want to keep it then you might as well just wear it and get it swapped at service time. Otherwise, pay the difference in exchange, get a new clasp and consider your watch no different than it was before your son made this mistake.
Good luck.
