I'm not sure how long it's been on their website - since there are comments on the page since June 2012... but now it's in Previews! Today Diamond published the December 2014 catalog for February 2015 and on page 438 is an ad for welovefine.com 's Retro Northstar T-shirt. They only show the white one for sale but on their website you can see the red and the blue one. Here is the blue one:

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Here's a link to the welovefine page or you can order it through your local comic shop!