It is very easy to make temporary replacement spokes. All you need is a pair of pliers w/cutters and a spoke slightly longer than the original. Use the pliers to bend an elbow at the same point as the elbow on the broken spoke, then cut it off so the length after the bend is slightly more then the width of the hub flange. Make the bend a wee bit tighter than 90 degrees. With some effort you should be able to get the spoke into place without removing the cassette. I assume the dogleg spoke idea works the same, but no need for a specialized tools.