My question for you is, where those breeders breeding deer-heads reputable breeders?

My guess is probably No. I'm not a Chi person but my guess is that deerheads are probably shunned in the show ring. For one thing, the whole point of conformation is to preserve the breed as it once was/is. If the AKC does not recognize deerheads, then it is apparent that the Chihuahua Club of America does not believe deerheads represent a "true" Chihuahua.

The standard calls for a well domed head, and these would be your "appleheads". Thus, all "deerheaded" Chis will not win in the ring. You're absolutely right when you say reputable breeders will not breed for "deerheads" as they are not recognized in the standard. I'm sure if you buy a Chihuahua conformation book, there will be plenty of old black and white pictures showing the gradual 'refinement' of the breed and breed standard. Personally, I'd stay away from anyone declaring they have a rare headed Chi for sale.