Some folks here have made them. If you have the tools it wouldn't be too difficult. If you don't get any more leads you could try a local machine shop and see if they can make you one.
I used one of these on a recent guitar, but I used it for side mount jacks:http://www.amazon.com/Grizzly-H5999-Jac ... jack+plate
They come in chrome or brass colored. I had to bend a little to the guitar shape, and it wouldn't be difficult to flatten it out. It may fit okay, I'm not sure. It looks like it would be close.