As someone who watches (and buys) retro EPCOT Center shirts on eBay, I can tell you all a few things.
First, there is a 99.9% chance the link SewIn2Disney posted is the correct shirt; unless there is some other shirt almost identical to it that I've never seen.
Second, although you may think the quality of Disney merchandise has gone down over the years, the yellow shirt was originally very thin and very prone to shrinking. Unless they emulated the material of the shirt too, a new one is likely to be of higher quality.
Third, due to the shrinking, and the general style of tighter shirts back when the yellow one was released, anyone who wears a size L or greater would have a tough time fitting into one of the older shirts. I normally wear a size Small, and when I order the vintage shirts, I get large usually, and those fit me well.
Cool find! Hopefully they will release a blue, "21st Century starts..." with SSE (most of you should know the design about which I'm talking) shirt soon. In my opinion, that one is best!
EDIT: Or maybe they will start selling this shirt (my all time favorite and top 'steal' off eBay at only $10.49 plus shipping!):