Jumpsuits like dungarees can be really good for breastfeeding especially the ones with buttons down the front.  They look cool and as its an all in one you don't have to find a top to wear!

Here are a few long sleeved ones with front opening access.

Same vest trick - open the front of the jump suit, pull vest down, pop nipple out.

Atterley Road £75 / Theory £290 / Gestuz £119 / Whistles £170