Heh, interesting, probably my misunderstanding on your last sentence, but just to make it clear - the orange pumpkins are the ones you need for the banitsa :) Plenty of them all around the country - http://navigator.receptite.com/wp-content/uploads/2010/10/tikva-cigulka.jpg , we call them цигулка (the one on the picture) and свинска (probably different shape, no idea, honestly I never got the difference...). 

And the green ones you bake, puree, etc. BTW I hope you don't throw the pumpkins seed, do you? We never do, we just roast them no matter what the pumpkin is :)

Actually it shouldn't be very difficult to find orange pumpkins in Sofia - I am sure you are familiar with all those people selling in random places and depending on the season cabbage, water melons, xmas trees, pumpkins, etc. Usually when there are green pumpkins, there will be also orange ones, just ask them for цигулка haha, and you are on your way to your баница с тиква :)