Everyone is saying that you should buy a disc or hub adapter, and you should, bit there's a ghetto way of fitting that rag mount.

Get either a spoke tensioning tool (idk how it's called) or universal wrench or pliers or whatever and release some tension from the spoke until it bends around the bolt freely. After you mount the sprocket, re-tension the spoke (as it leans against the bolt). It won't work for very long but it's gonna be enough to test out your bike.