Historically I had a Minolta Slide Scanner (using SCSI board) and further to that an Epson flat bed scanner bought after research for 6×6 cm scanning, Moving on from ‘history’ you should consider the use of something like an Ohnar Slide Duplicator with your DSLR. The duplicators should still be around as S/H items or you could go to SRB (UK company that makes one of these ) at just short of £60). They reccomend the use of the 18 to 55 mm lens on the DSLR used for the job.SRB make adapters for lots of photo kit.
British Astronomical Association
Supporting amateur astronomers since 1890