I remembered such a t-shirt given as gift on an Amiga German Magazine if you buy game package for C64 or Amiga, but not directly as Amiga related gift, just game gift.
Was it Marble Madness or something similar?
_________________ "When the Amiga came out, everyone [at Apple] was scared as hell."(J.L. Gassée, former CEO of Apple France and chief of devs of Mac II-fx, interviewed by Amazing Computing, Nov 1996).