I recovered mine 30+ years ago with leather. I bought a hide at a Tandy store and used contact cement. After it was covered I trimmed off the excess, leaving enough to tuck around the edges and glue to the back/bottom. Mine has a fluted hole too. Using real leather gave me enough stretch and pliability to form it into those areas, and stretched tight looks really good.
I am not using that part right now though, because I wanted to put a different radio in and did not want to destroy it in case I wanted to go back, so I used one from a TR6 that was already cut out for a big radio.
Dan B.