scanner or ... you could stitch together a mosaic of 4 or 3x3 photos taken at a distance of 30cm like you did with that gorgeous spider.
There's mosaic software people are using for milky way mosaics. Lo and behold, Wiki has even a comparison table for that.
https://en.wikipedia.org/wiki/Compar...ching_software
I never stitched a mosaic but I assume it could solve your challenge of digitising your beautiful sketches. Prop them against a wall or on an easel, camera on a tripod real close and take the photos with overlapping areas at the "seams".