Yesterday I called up my kid brother from work and asked him to go to a real electrical supply house near his neighborhood to pick up two new ones (UL listed and mfg by West Port Mfg. in USA).
He paid US$1.25 for each and they appear to be made out of vinyl instead of vulcanized rubber. Construction seems decent...except they use 16AWG TFF stranded instead of the usual 14AWG stranded for the pigtails.
The cheap-cheezey (non-UL) listed black rubber sockets from China that I see in hardware stores across town are $2 and change. I think I saw one place selling them for $2.79 (
There's one company (Cooper, I believe) that makes them out of BAKELITE! I've been trying to score one...but no luck, so far -- two of the supply houses I called don't carry those -- one doesn't even carry any type of lampholder.
These bakelite ones are the ones used normally in making those lighting strings I mentioned for use in the subway during construction.
Today I was in a job-lot surplus store that was selling Mexican Leviton rubber sockets for like US$2.50 or so.