[Source] Findings suppliers

Frei and Borel sells the older style tube type pin assembly you describe.
Even the smaller size is not cheap. A buy when the labor to duplicate is
pondered. No losses or dissatisfaction to report. Installed half a dozen
over the last 10 plus years.
Tim

I know that Frei & Borel supplies joint assemblies and pinstems in 18k
yellow and 18k white. They also stock those great push pull safety
catches, the ones with the tube that pulls open and pushes closed. They
also have double brooch assemblies, which seem pretty secure, since you
have 2 pins instead of just one. You might call them to see if they ever
supply these in 14k. Their # is 1 800 772 3456. -Jodi

Chaitana, Stullers in Lafayette LA has what I believe you are looking for.
They are on the web at stuller.com. Hit private site. The user name is
stuller and the password is mounting, maybe you can see a picture of it,
not sure never tried it. It’s item #1094 on pg. 354 of their findings
catalog. If you want a catolog their 800 # is 800 877 7777. You will have
to provide them with a tax number and 2 invoices from other suppliers to
set up an account to order. Good luck. Dess

I would highly recommend Boston Gem & Findings. They have a wonderful,
knowledgeable staff and are very efficient. Try them! 800 225-2436

        Does anyone know of a findings house that stocks better than
normal findings.... 

A. Herschlag Inc. Otherwise knowns as Herschlag’s–a high end findings
source.

21 West 47th Street
NY, NY  10036
1-800-223-6885

Good hunting,
Jessica