Do you mean Osamu Tezuka's Hinotori?
I googled in Japanese,but I couldn't find anything for sale now,though I could find old posters, some of them are for promotion, in auction site.
http://www.bidders.co.jp/item/111942581
http://page13.auctions.yahoo.co.jp/jp/auction/r67479650
Even ANIMATE(the largest retailer of anime in Japan) doesn't deal in the stuffs of Hinotori now.You can buy only manga,anime DVD.
I don't think Otakus want to buy a large size poster of the bird in the old anime.I think they need that of girls or boys or mecha.