I'd keep looking for a match. One of those marine stores that looks like a hurricane damaged flea market would probably yield the best results. They'll probably have three of 'em they've been looking to move for twenty years.(g)
Failing that, you can pick up some stainless steel plate and drill it to match your deck holes and the drill it to match your new cleat. You'll have to do some countersinking. I'd probably not go that route, though. I'd probably replace the other similar cleats as well on the theory that they are fatigued also. Plug your holes with thickened epoxy, drill new holes, epoxying them, and bed the new cleats.
I am unaware of any undrilled cleats. I suspect that manufacturers drill all their cleats and avoid any possible problems associated with mis-mounting.
For the above idea, and improved strength, you could also use a piece of teak between the cleat and the stainless.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.