T-shirts in sport programmers world are impossible to buy. T-shirt is usually prize or  souvenir

i somehow dont agree to the fact that a mere t-shirt is used to differentiate between a great coder and a mere nobody like me .

a great coder is great by his/her skills and not what he or she wears.
 
besides the idea  of t-shirt came up just as a codeforces fan club t-shirt .
there can be div1 div2 t-shirts  if differentiation is required between div1 and div2 coders  :)

In my opinion ,t-shirts can be given to say(some top 5 or 3) coders in each division in each round .May be that will motivate and inspire others too.And yeputons and pistone both should agree on this.)