I'm looking for the same part and gave up finding one used. I don't know how badly yours is scratched, but I've decided to have mine refinished to remove glue we got on the inside of the cover. Going to do both sides to clean up some crazing that's happened with age as well. There is a tutorial somewhere on LT on how to do it and the results can be pretty striking.
FWIW, have a used passenger side H/L housing with lens and embellisher ring for 2005 Elise. The clear coat over the black at the top is deteriorated, not uncommon. For that matter I also have a driver side one without embellisher ring that needs to have the lens reattached to the housing.
See For Sale Listing : http://www.lotustalk.com/forums/f95/headlamp-lens-housings-209866/