i have one of g&t's manifolds, and the impression i got when i bought it 2 years ago was that he was frustrated with the experience of making M42 pieces, so i doubt he's likely to do so again-
but even if he did, there is no guarantee it'd be compatible with RHD cars.
i just moved, and i'll be getting mine out of storage in a couple weeks. if you'd like, i'll take pics of it then so you can at least have something for a local welder to replicate. let me know.