To the best of my knowledge they are not being reproduced. About 10 years ago Jim Carter was selling reproductions but no longer is. Then there was an eBay seller with a metal version he was selling, they looked similiar but not original.
I bought mine on eBay as GMC NOS about 10 years ago. The last complete set I heard of sell there was for $1350.....
Rumor on Stovebolt a couple of summers ago was that Pat Wilson was designing a reproduction set. Try emailing him at
patwilsondesign@nc.rr.com
He lists the cone lenses for these lights on his website
http://www.patwilsondesign.com/products2.html
1958 and 1959 GMC parking light cone lenses reproduced to exact likeness thru a mold process. $75.00 for the pair.