You could lock two full-sized nuts together on the other end of the axle and then get a full-sized spanner on those to turn against a full-sized spanner/vice on the locknut.
@ffm started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
You could lock two full-sized nuts together on the other end of the axle and then get a full-sized spanner on those to turn against a full-sized spanner/vice on the locknut.