The upgraded sockets are described by Bob Danielson here:
So I contacted 'bluechips2001' and asked about availability.
Here's his reply:
"Hello Lee, Sorry but the UK mfg. of those sockets went
out of business and we were not able to find a quality
replacement. Thanks for the inquiry, Joe"
So ... bummer, I thought those were a great upgrade. I have not found another
useful source. The original-style holders are available from Moss and TRF:
On Thu, May 21, 2020 11:19, Bob via 6pack wrote:
> Back when I was restoring my 72 in 2008 there was a vendor that sold
> replacement light sockets for the rear lights. As everyone knows the sockets
> supplied are not the best.
> I was just wondering if they are available from any of the US suppliers.
> I had to replace 2 bulbs today and I am thinking that maybe the reason
> they failed is the socket just does not hold the bulb that tight. I would like
> to replace the sockets with the upgraded version the next time I have to
> replace a bulb.