Molds

Chopped mat would be good.  I would buy a pair of headlights so you don't have to do it on your car every time.  Tape off EVERYTHING and spray it with pam.  Draw the shape of the eyelid with a sharpie on the tape.  If you're doing it a bunch, I would cut the shape out of posterboard to get it exact every time.  When you lay the fiberglass, go about 2" past the mark.  The marker will transfer from the tape to the fiberglass after it hardens.  Put 2-3 good layers on before you remove it.  After that, prep it for paint like you would any other fiberglass.

IMO that would be easier than making a mold.

http://www.geocities.com/placidwarrior_1/Ion_eyelids.html

I made my own eyelids, however i'm not sure if its the best way by using the light for every set unless u get yourself a spare set of lights.   I tried plaster of paris...not the greatest, however i had one guy tell me he had moulds made from truck bed liner spray.  He would send in his project and they would put a release agent on or whatever so nothing stuck, then they would spray on a few layers making it nice and thick, then they would add pieces of stick or something to give it some bulk and then spray some more and just build up a decent mould that way...sounds like something i would try if i had a mass order but when u sell only  a few here and there its not a big deal to just use the lights (just remember to mask well).

In my link i have attachment points but i also made a set that requires double sided adhesive.  I did a set of rear light covers for my car using 3M tape which still seem to be holding just fine.