Just thought I'd post about some T shirts Forever 21 have in at the moment.
The bad news (if you care about fabric) they are part polyester (but 55% cotton). The v neck could do with being a teensy bit lower. I also haven't washed them yet.
But... they are pretty cheap and definitely longer in length than average. I'm one of those with large norks (30FF) and a long back and there is plenty of room in a Small. I think I could have sized up fairly easily without looking shapeless if I'd wanted them to be slightly bigger, i.e. they are likewise not too baggy.
Good range of nice marl colours (they also have plain t shirts which look similar but I don't they are quite as long)