I got hold of a Sunagot Delus Slide Duplicator second hand online. It looks like it was made in the 1970s or 1980s, so pre-digital cameras, so a bit confused what it was designed for.
Anyway, it works a treat on my Canon 6D. It is not easy to fit the full image of the slide onto the sensor even when the zoon is set to 1x (the minimum). I tried adding an extension tube but then I can’t achieve focus. It is possible to fit it all in the frame, but it takes a bit of time. Some images need a bit of processing on the PC once captured as the contrast and saturation can be off as the image of NGC 604 below shows, but others like Mars come out well straight from the camera. So in all I am VERY pleased with this method and look forward to digitising some slides to help someone prepare for a talk, and also to keep their slides for prosperity sake. [the slides below are comercially available ones I also got second handfrom ebay to do some testing; NGC 604 The Planetarium Armagh; Springtime Dust Storm Swirls at Martian North Pole, The Planetarium Armagh; The Sun, slide 679/10 Astronomy Slides, Rickitt Encyclopedia of Slides 1973]
Thanks for the ideas.