I found some posters for Jack! A nice lady who lives in Singapore saw my post about searching and left a comment about where to look. Just like she said there would be, I found a poster store at the massive Suntec City Mall. It had so much stuff they had a catalog that you look through to pick which poster you want and then they get it from the rack behind the counter. Good times!
Many thanks to Kathy the Kiwi. I owe you one.