A long shot, but...
John Gerber's former shop is one block* from the house where I now live in Davenport, Iowa. In 1999 I interviewed his widow Rose for an "SOSS" article I later wrote. Mrs. Gerber was as sharp as a tack, even though she was past 90 (she has since passed away, of course). She took my friend and me on a tour of John's workshop, which is still standing, but cleared out of speed goodies. John had died of cancer in 1979 and Rose kept the shop as if he had just shut off the lights and gone to bed. WOW! I expected John Gerber to walk in at any moment and start grinding crankshafts. One was still in the lathe awaiting finish work! Lots of speed goodies everywhere, including Gerber rods hanging on the wall. Rose said that when she passed, everything was to be donated to the National Sprint Car Hall of Fame and Museum in Knoxville, Iowa. So, I assume that the rods and all John's speed goodies are there now, either on display or in storage. PERHAPS one could buy extra Gerber rods from them? I don't know if the museum will sell donated parts, but it's worth asking.
Marshall
* Make that "TWO blocks", if it matters at all.