I did a google search for the hypercolor shirts, and found an article saying that Land's End occasionally sells them under the brand name Chromicolor. Went to the Land's End site, did a search for Chromicolor, and got that. No adult sizes, though...

Searching for Chromicolor with google, I did find a wholesale producer, but the minimum order is something like 20 dozen, so I passed it by... Land's End has an option to send you color swatches, though...