Maybe inquire on the Morelia Viridis Forum?? There are many GTP breeders there and they may be able to point you in the right direction.
If I may say, blue GTPs are few and far between. Most breeders who produce a neonate that turns out to be a true blue gtp aren't going to let it go. They may sell a neonate that has a good chance of developing the blue color, but a) you're going to pay a pretty price and b) you're still taking a chance as there's no garuantee a neo will develop blue coloration at all.
Those are just some things to consider in your search. I wish you luck and if you do find one, you have to post pictures here!!!
Also check the classifieds at www.kingsnake.com there are some reputable sellers on there that are listing Blue Adults every so often, but they aren't giving them away, last one I saw up was in the 2000 range!
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Retics are my passion. Just ask.