the serious hardened steel heavy Chain left at the school Bike rack remains a choice..

maybe a Banjo bolt will keep the axle from slipping if you cant get things tight enough..

scrolling down, Peter has solid axle rear pits listed for alfine 9.5mm & Rohloff 10mm solid axles , says 1 side pit-locked will do.
they are Nut substitutes not skewers..