I don't know what your marina quoted you but the Edson wheel brake system cost me $209.00 at mine - Worth every penny.the price made my eye's glaze over. thier has to be an alternate.
I'm talking about single handing under sail. The ability to lock the wheel is huge. As for the auto pilot, if he thought the brake was spendy that should really make him blink.I assume you are not talking about "while at anchor" as that is a no brainer; use a line.
This is an excellent time to broach the subject of getting an auto pilot for the boat with the Admiral don't you think?