A friend of mine (a video assist / occasional cam assist) has started manufacturing decent quality, bespoke 3G SDI BNC cables:
He uses RG179 cable and can make them in a variety of colours, lengths, and offers to add your name/logo/details to the cable. I personally use them and they are very strong/last well:
Or if you prefer a basic cable (not coloured) then he offers a slightly cheaper version here:
He also provides invoices - see listing for details.
Matt Choules GBCT
1st AC / Focus Puller
London / UK