I just found stuff at Goodwill tonight! I found a maternity tank top and a large (non-maternity) skirt. The skirt is dark brown, so no big deal if it gets dirty, and it's a stretchy cotton knit. Kind of like a really thick t-shirt material. I HATE the hospital gowns and I figure if I want to walk around, even outside the hospital if it's a nice day, I don't want to be in a pair of DH's boxers. I think this will be pretty comfy until the end, when I usually want to be naked. And, I spent $4 total on my whole outfit, so if I just need to toss everything afterwards, no biggie.
I also picked up a 3 pack of cheapo tank tops at Sam's club. If I want to wear something in the tub, I figure I could wear one of those and still have one or two dry ones to change into if I get out.