Bear in mind the photo at right is what we're after for original appearance. Photos below are courtesy of Mark Wellard in Australia. These triangular hinges come from an MG Y-type and appear to be the same parts used for the MGA Coupe. Aside from the hinges, the Y-type visors are NOT the same as MGA parts.

Hinges for MG Y-type
and MGA.

Addendum 28 NOV 2021:
Peter Hackney in Australia reports a different possible part number for this triangular hinge, 7/28988-9 referred to as a"Friction Hinge Visor Bracket". Last purchased in Australia around 10 or so years ago (circa 2011) for a colleague, but when recently trying to get them for another chap, the company, who were a general hardware seller, they had closed. Another seller of similar product lines said that they were no longer made.

Others have suggested that an Austin A30 visor is also the same as an MGA coupe, but not so. See pictures below. They have a plastic-welded or heat-sealed edge and are made with the same material as used in the MGA coupe headlining. They would make a suitable visor for the coupe because of the headlining match (if you still have the correct material), however, the hinges are totally different.

Visors from an Austin A30 with similar fabric but different hinges and heat sealed edges.