If there is a broker involved, and they don’t own the boat then the bill of sale should be between the two parties, I don’t see how you can avoid the other party having your contact details in that case.
At least when we sold ours via a broker, that’s exactly what was the case and they used the industry’s standard marine contracts. The only time this would be not the case is if the broker is selling it, at which point the details would be of the person/company selling it.
The broker under normal circumstances isn’t selling the boat, just acting as an agreed intermediary between two parties.
