I test folded the diagrams for this charming little guy (yes, I said charming; call me crazy, I love bats!) and just in time for Halloween, Nishikawa-san has put the instructions up for sale at OrigamiUSA‘s online store, the Source, here. (Support an origami artist! Just US$2! Less if you’re an OrigamiUSA member!) With giant ears, a fun shape and color-change eyes and mouth, it’s well worth folding.
The piece looks deceptively simple, what with all that smooth body and wing area… this is, however, a high-intermediate piece, so I’m not sure I’d recommend it for a beginner. A 25 cm (approx 10 inch) square will yield a bat with a 20 cm (approx 8 inch) wingspan. Regular commercial origami paper works just fine, and you definitely want something with a contrasting backside color to show off the eyes and mouth.
(If you’re interested in seeing more of his work, this is the listing of all the pieces for sale through OrigamiUSA. And his book “Works of Seiji Nishikawa” is still for sale via the Gallery Origami House website (English page, with shipping info); see photos of all the pieces in the book here (Japanese page). It’s also available through Nicolas Terry’s origami-shop.com, here.