I think spruce has some, but the TSO ones are PRICEY. Are you sure the Ercoupe requires TSO instruments? There was quite a discussion about the TSO requirement for certified aircraft on the Cardinal Flyers e-mail digest a year or so ago. The general gist of it was, if the aircraft didn't originally come with TSO instruments, replacements don't have to be TSO. Given the vintage of the ERCO, I'd guess that it might not have come with them orginally.
On another note, I've been working on a friends 1947 415C/D for a couple years now. I've got about 5 hours in Ercoupes and love them. We're working on an idea to convert a project on into tandem seating

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