Hmm, fairly thin so quick and easy to 3d print.
And I've used pretty stiff rubber filament. for a variety of things from gutter seals to miniature rubber tires (3mm diameter)

The ony issue you'd have with fdm printed rubber would be that the surface is never going to be completely smooth.
And that's something that will probably come out during printing.

How thick/high/tall are the letters on the marginals ?