Another option is a "Wheels Manufacturing emergency gear hanger" similar to the linked ghost hanger above, these come in around 4 - 4.2mm thick alu and simply slip over the axle hole and are held in place by the Q/R nut, you might need a longer skewer. The downside is when you remove the rear wheel the hanger&mech drops free too, but it could be worth looking into.
I have used one with a 10mm bolt through axle, when set and in place, brilliant, 3 hands while setting up would be nice but i managed ok. Gear shifting seemed fine when taking a wheel off and back on again, indexing stayed put.
What freezing77 said.
Another option is a "Wheels Manufacturing emergency gear hanger" similar to the linked ghost hanger above, these come in around 4 - 4.2mm thick alu and simply slip over the axle hole and are held in place by the Q/R nut, you might need a longer skewer. The downside is when you remove the rear wheel the hanger&mech drops free too, but it could be worth looking into.
I have used one with a 10mm bolt through axle, when set and in place, brilliant, 3 hands while setting up would be nice but i managed ok. Gear shifting seemed fine when taking a wheel off and back on again, indexing stayed put.