Can anyone put me in touch with the aforementioned item?

There's two possible things you could be referring to. One, TI makes their own giant posters with their graphing calculators on them, and they tend to give them away at teaching conferences (I got a few at T^3 2013). Two, you might want to make your own poster. I have my own painstakingly-created vector versions of the TI-83+ and TI-84+ calculators in black-and-white, and those would certainly be suited to posters. What's your use case?