Before having someone make custom fittings for your boat check all of your options first. It shouldn't be difficult to find the deck hardware in the size you need. I noticed that most deck hardware is sized in (MM) millimeters so measure accordingly.
A pack of cleats in the size you want might cost $5.00 plus shipping but if you have someone custom make it for you it might cost $150 plus shipping. That is a large sum of money for things that can readily be found.
In addition to naturecoast, try:
One or more of these sources will have the fittings you are looking for. I have orderedfittings from just about all of these companies in addition to naturecoast that advanced builder mentioned above.