There are two styles of that knob which I've encountered. One is the splined - used on our FT-980s. The other is flatted - and this is seen on other Yaesu models such as the FT-757/FC-757.
What I would consider is finding a length of 6mm diameter aluminum shaft that you can contour and groove so it approximates the OEM splined part. Then, machine a flat on the panel end to allow a 757-series selector knob to be used. Sets of these knobs come up somewhat frequently on the auction site.
Keep the splined shaft for future use or sell it to someone whose rig was damaged in shipping, as they sometimes get broken as the result of a clueless packing job.
73 - Fred, N8YX
