Tumblr user shootforthemoonmoon recently recommended ordering these Aperture Science towels from Quantum Stitching on Etsy.  These add another great accent to my Portal Bathroom!

They normally come in white with black stitching, but they were able to get me the inverse!  They look great, and I got them in less than two weeks (and they shipped from Canada, too!).  I highly recommend their shop, and thanks again to shootforthemoonmoonfor the recommendation!