You're absolutely right about not wanting to let a Fulvia go after you've got one. And they certainly are thin on the ground over here.
My strategy was to look for quite a while and then give up in frustration. As soon as I starting looking for an Alfa Stepnose or first series 124 Coupe instead, my Fulvia appeared. So you may want to feign interest in, say, Borgward Isabellas Coupes, to see if you can flush a Fulvia out that way.
If you're game for the strategy Huib suggests (take an obviously bad car and do it up right), there's a Series 1 candidate here in the Bay Area that Jaan Hjorth is selling on behalf of the owner:
http://www.eddinsmoto.com/id117.htm
I've seen this one briefly. Seems to have substantial rust, and needs upholstery work. Don't know how many takers it'll get for the asking price in that shape.
And if you're willing to bend your no Zagato rule, there's also a nice usable looking 71 Fulvia Sport Coupe with a 1.6 liter motor available at Fantasy Junction:
http://www.fantasyjunction.com/used-car ... 6c0770a36c
Haven't seen this one, but have daydreamed about having it in the garage next to my 67 Coupe Rallye.
Good luck with your search!