my sense is that there would not be many, if any, EP sneaky shafts available.
Your link says you are unsure if it is, in fact, a Prewitt.
if it were me I would def get in touch with Ed to first establish for sure if this is one of his and, if so, what bwould he charge to make a new shaft for it. This would be ideal.
Or you can simply adjust your sights a little and look for a shaft from another maker with that same pin (looks like a 3/8 10) and plain brown phenolic.
Something to consider whether Ed or anyone else might make a new shaft, if you ever decide to go that route, is that brown phenolic can be tough to match because the new phenolic when cut will be a different color than that which has some age (patina) on it. Even if it came from the same orig supply.
Whatever way you decide to go, good luck with it.
it would be key to find out if it's actually an EP, imo.
best,
brian kc