Bruce,
Great advice from Dan R. These cars were out of production, most brands 20+ years ago. Although MG Magic in Miami, FL has stockpiled some TD Replica parts, any tops they’d have are going to be that old and vinyl doesn’t age well.
As far as getting a frame, MG Magic might help, but getting your top (material part) made by a local upholsterer/convertible top shop is the way to go. Having the old top for a pattern is good, but most better shops will be able to work from good pictures showing several angles.