Get this groovy long-sleeved t-shirt. Many sizes, short-sleeve, baby doll, even maternity style. Bags, mugs, hats too. The one shown here is $18.99 from CafePress.
According to the manufacturer:
The most comfortable t-shirt ever! Our 100% cotton, Hanes Beefy-T is preshrunk, durable and guaranteed.
6.1 oz. 100% luxuriously soft ring spun cotton
Ribbed sleeve cuffs