Wheelcovers: Original or reproduction TD caps will not fit the VW wheel. I came close (not exact but close) with chrome VW hubcaps, which I drilled to fit the MD wheel centers. You can see them on my car in the photo gallery, PMOSSBERG folder
Steering Wheel – Grant makes a number of banjo type steering wheel and sells a VW column adapter. Close to original, not exact, but probably the closest you will find. Go to http://www.grantproducts.com/ and search for “banjo”
Grills – Chrome slats were avaialble for original TDs. You are right that the standard was painted slats, but not only to match the exterior. They often were matched to the interior of the car.
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)