You also asked about a dash rear-view mirror. The Duchess kit came with an original type TD mirror. I found it unusable as it did not provide much adjustment range. I replaced it with the type typically used in Cobra kits.
One source is Shell Valley. It’s $20. You’ll find it here: (9th item down on the page) http://www.shellvalley.com/Store/products.asp?ID=Accessories &store=cobra
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)