that was me
we took a sheet of a plastic diffuser (thats what the guy at lowes called it when i explained what it was) for floresent lights he got at lowes, then took out his amber corners and cut out the general shape make sure to leave it a little larger than the orignal. then i used a heat gun to heat up the clear piece while laying it over the amber piece to give it the correct shape. after we got the shape right i took a dremel and cut it as close to size as i could then just used a little epoxy to hold them in
it took a few attemps to get it right, but a sheet was like $5 and was 2'x3' so there was enough to make like 10 or 15 pieces
the end result was pretty good, it wasnt perfect, there was a little bit of "wave" that i couldnt get out (it wasnt my car, and i wasnt getting paid so i got it close enough for goverment work) but you had to get VERY close to notice (like you had to bend over to get a closer look before you seen it)
i never tried to make a better set for mine because i liked how it looked without lenses better, only after i got bulbs that where chrome when they where off (kinda like siverstars but they didnt turn greenish yellow after a while)