There's no such thing, due to non-standard vertical staggering, unusual shape of the case itself and long travel of Cherry MX switches. I'd love to have a TM2030-like skin though, because it dampens noise (especially upstroke) and prevents dust, water and snacks from entering the board... I don't type all the time.
However, special thin (PE) foils w/ a rubber band on the perimeter do exist and are meant for use with keyboards in the health-care industry. They're designed to be placed on full-size keyboards though... You'd have to make your own ghetto one (two, actually) for the ergodox.