What exactly are you looking for? Still not 100% clear. Are you looking for something like a tonneau cover like old British cars and miata's had where it covers whole interior and dash but leaves windshield exposed (usually allows you to unzip and drive with most interior covered)? Or what I've typically seen in the corvette world where you have a mini sized car cover that essentially covers same area but also covers windshield? Or something totally different? See links below then clarify. To me I don't believe you are extending the life of the top by leaving retracted/folded 24-7-365. Likely the time you do you to put top up after spending years folded it will just rip.
Robbins Vinyl Tonneau Cover - Blue for 99-05 (not mazdaspeed) for Miata 1999-2005, NOT MazdaSpeed
1953-1955 Corvette Cockpit Cover - Corvette Accessories Online