So you've hit up Etsy and Shirt.Woot. They didn't have what you want, not tees weren't indie enough for you, what ever. Don't worry, I have plenty more online stores up my sleeves.
But for now, I'd like to stray away from ironic indie tees, and talk to you about vintage apparel. Vintage tee shirts, are great for several reasons. One, they are indie as all get out. Two, they cut down on environmental waste.
Where to buy vintage? The answer might surprise you if you haven't shopped vintage before.
Thriftshops such as Goodwill and Salvation Army tend to have some vintage tees. But you have to check early and often to find them before the other hipsters do! There may also be some independent thriftshops in your area.
Vintage indie t shirts include, but are not limited to: old sports team tees, mission trip tees, event tees. All old, all indie.
Good luck on your indie t shirt hunt!!!!!