Might help of we knew what country you are in...

If you are in Australia a good starting point might be Huber and Suhner.
I think they are also elsewhere in the world.

A web search turns up quite a few hits for supplying the part numbers
mentioned.

Cheers Bob W5/VK2YQA

wrote:

I want to buy non typical coax like RD316 (double screened RG316) and
RG223.

I can get some from RS, but surely there must be a coax cable vendor I
can go to.

I had a damn good google and come up fruitless.

Anyone help??

73s