"You can order a replacement from C F Martin & Co. for a very reasonable price.

Only the cheapo ones, not the nice Delmar pick-guards. For those, you need to order through a CFM Authorised Service Centre. I've replaced three of the cheapo pixellated-pepperoni-guards on my Martins with Delmars. CFM would not supply me direct, I had to go to an Authorised Service Centre each time.

On reflection, a D-35 pick-guard will be black, so you might get a black one from CFM (mine are all faux-tortoise). If you order a pick-guard, remember that rosette-sizes vary between models, so you need to make sure you're getting the right one for a D-35 rosette (or be prepared to do some scraping/sanding to adjust the guard to fit.

Alternatively, you could buy a sheet of the black material and make your own guard, using the old one as a template.