Where can I get the specifications for an ISIS hub? width, length, diameter etc. I’ve found some threads about it, but nothing but images without dimensions and lots of broken links. Anything will probably be helpful. 
This is probably a good start http://ebike.hu/download/016b02d6df2bb9a1.pdf/ . Beyond that, the only standardised uni specific stuff is the total length of the axle and the spacing of the bearings - normal hubs have bearings which are 100mm apart centre to centre, here’s the spec for the bearing dimensions http://www.unicycle.uk.com/unicycle-spares/hubs-bearings/unicycle-bearings-pair-isis-42mm.html . No idea on axle length - easiest would be to just measure one!
Great start, thnx!