If you don't mind going outside of the wargaming realm, there's a company that does mostly model train stuff called Micro Mark.
They have a small range of linked chains that you can find here:
https://www.micromark.com/Miniature-Chain-for-Model-Work
I'd suggest size E based on the conversion from inches to
mm. That would put you fairly close to
40k style scale.
Hope that helps some.