I bought that one when it was out, and don't remember it being terribly rare. If I remember correctly, we had it in stock at Dolphins of Hollywood, and I think they had it at Sam's, Flash, and Pat's as well.
I think I remember seeing it in Chicago, too, at United Distributors. I never thought of it as "rare". I saw it a lot more on store stocker than on white DJ (which, ironically with regard to this thread, I WOULD have considered "rare"). I guess the recent rarity of 45s depends a LOT on how many of the original pressings got destroyed by the early 1970s.
I'd be curious to hear from The Yank if he remembers seeing stockers of the Dee Dee Barnes in Chicagoland record shops around the time it was out.