It is a "feature" of boats that they are ( very ) short production runs. It is unusual to sell "tens of thousands" of a particular make, model, style. That means that for most boats, "things that don't break" are generally made to order, in the exact quantity for the production run. There are no "spares" manufactured.
About the best you can do is "find something available that will fit" or have a replacement custom manufactured, just for you.
It is simply the way modern boating works.
In past days, all boats were "one offs", everything on board was custom fit to that one boat, but there were craftsmen all over the place who could do such work. ( and re-furb your kitchen at the same time! ).
Which is why you get the standard reply, "find something that fits/works". It is the only rational cost effective thing to do.
If there are many boats in the same make, model, year as yours, possibly you can find a junk one. More likely, the junk ones are abandoned somewhere, sunk, or have met up with a chainsaw/sawzall. Which, brings us back to "find something that will cover the hole and you can paint over it kind of response.
Only other potential solution would be to contact a company such as Piedmont Plastics, who sell to small production boat mfgrs, and they might be able to point you at someone who would welcome the work.
Good luck.
