You can buy the Hansa brand individual round plastic covers for the 5 3/4" lights. Far better looking than the bits of flat perspex that were a common add-on years ago on the RS's. The flat bits of perspex still let the dust in behind them onto the lights whereas the individual covers actually keep the dust out as well as protecting the lights. I remember some wan#*%s even used coloured perspex years ago.
SFE.