This is an easy one
Hank Moody wears either a plain t-shirt (black or navy blue) or a dark long sleeved dress shirt (black, navy blue or dark gray).
Although you can occasionally see him wearing a white t-shirt and once even a pink polo shirt it’s usually because he has to wear someone else’s shirt.
Lucky for you I’ve searched for and found the ones on Amazon:
Get Hank Moody’s Calvin Klein Men’s Regular-Fit Stretch Herringbone Dress Shirt
or Get Hank’s Hanes 4 Oz Nano-T Cool Dri T-Shirt