I have found a source that has lot’s of 14K gold-fill items including
wire, sheet, tubing, and findings in both yellow- and rose-gold fill.
I actually posted earlier today asking if anyone had any personal
knowledge of the company. They are called Pasternak Findings and are
located in Israel. If you order $500 or more, shipping is free; less
than $500, shipping is $27. Their pricing on Sterling seem very
competitive, but the gold fill seems quite high to me. I am planning
to contact them to discuss their pricing and make sure I have not
misunderstood something. The problem is, they are the only source I
have found for gold fill tubing.
Take a look at their site pasternakfindings.com.