Hi, make a template in aluminium, bend to shape, place the perspex sheet piece over the ‘mould’, heat gently with heatgun and the perspex will fold over mould to shape, file and sand to suit...
You could try Southern GT or Tornado, both in the U.K.
or reach out to Roy Snook on this forum, he used to make them, supplied oversize and you fettle and fit as required.
Or fromUSA Mark Clapp