I propose transparent acrylic wrist rests for TKL and perhaps full-sized keyboards. Something like what Ducky Nordic has been demonstrating. Not too wide, but comfortably wide, with a curvature or some slanting along the front. I believe there's merit for an easily-to-clean wrist rest that goes with any keyboard in terms of color and style. I like my leather Ducky wrist rest, but that "leather" shows wear and dust/dirt quite easily, while being difficult to clean.
I'd make it taller: it needs to be the same height as an average FilcoDucky keyboard front case height and with some slant at the front if possible, a bit of a trapezoidal wedge along the top. Doesn't need to have any logos etched onto it or be as wide.
Basically something like this, but made of acrylic (though wood would be cool too, just not as universally matching)