I tried two different things with mine. On one I drilled the old knob off and replaced it with one I got on ebay. They're getting more handles and knobs there every day. The other one I replaced the handle with one from a like sizes Saragosa. The 14000 sized Saragosa handle was a little bit over $70 if I remember correctly. Some Stella handles will fit, but are around $140. Koose Tackle on ebay has some nice handles and knobs. Another dealer has knobs that look like JM handles for $35. Alan Tani (alantani.com) also has some knobs for sale. You can also try here:
I decided that the way I fish my Spheros, the existing handle is okay. I don't crank in, I use leverage to gain line, then wind down. When working a lure, I am just using first finger and thumb on the knob anyway. I still don't like it, but I guess I have learned to live with it.