Lomography's Digitaliza scanning mask for 35mm film, which I should be using to assist with digitising all of last year's (still missing) Blips. But there are too many other things needing done, and other excuses. At least this gadget seems to tick all the boxes for my desired purpose, as does their version for 120 (medium format) film. 

Thank you to micro43, as I've also sourced the same (or very similar) light box as shown in your recent Blip. It seems great, and is much more evenly lit than the one that Intrepid Cameras have in their enlarger kit... the one they sent out with a couple of obvious scratches in the light surface.