Alf - I got your email - I've been travelling. Looks like you found Bill's number. The ERA ducts also do not have the little tab on them. I can't recall if they are painted, or just use tinted resin, but they are symetrical...
Being as my FIA build may be 2 yrs off, I will sell you my Kemper mades for what I paid - I think $150 +-.
Alternately, try Kirkham - as I said, they looked identical to the Kempers.