I would really love to wear this watch as a dress piece but I wish it was a bit thinner. Does anybody know if there's an aftermarket non-exhibition case back that fits this model?

Thanks in advance!

There isn’t. You’d need to cobble together fifty or so orders for a custom run.

Note, the non-exhibit caseback of the similar model C65 Sandhurst is only 0.1mm thinner at 11.6mm compared to the Dune at 11.7mm.I think the size factor is the automatic movement and its rotor more so than the open view case.