MG Magic is still in business. Here’s their web site:
https://mgmagicclassicmotorparts.com/
There is no source specifically for the Classic Roadsters Ltd. Duchess that I am aware of.
The Duchess uses a reproduction TD grill. Even Moss Motors does not have them. Occasionally you will see one pop up on eBay, typically in the $1,000 range if they are in any kind of decent shape.
A good, make that very good, metal worker may be able to repair your shell.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)