Here you go. Looks like it would cost around $50:
https://www.pasternack.com/rca-male-rca-male-pe-b159-rd-cable-assembly-pe38134-rd-p.aspxSame vendor that Nonoise linked to, but the cable shown at the link he provided does not have the correct impedance or the correct connectors.
Does 75 ohm really matter for a digital coax cable or would a standard RCA cable be just fine??
Some members here have reported using analog cables having unspecified impedances for digital applications, with results that were satisfactory to them. IMO, though, it would amount to introducing a known design error into the system, with sonic consequences that are equipment dependent and unpredictable. In other words, from a technical standpoint it is very poor practice IMO, even though it might happen to work out ok in some systems.
Regards,
-- Al