Lowe's does not carry it but they can special order it for you. I have no idea if they can get cell cast acrylic though. As far as putting 2 pieces together, I have no idea but I dont think you would get the same strength as a single 1/2" piece.
Thanks for the ideas, Ive been very busy of late, doing Marine stuff. I dont recall any windows on the dirtwood, I mean driftwood, LOL. I have found a glass place that can get me 3/8x 8'x 2'. Im gonna try it. Really wish it was thicker but running out of patience, wanna get it done and get the old lady off my butt, HAHA.