No idea what an ISBN number is, but I can tell you this:

"Honda NSR250R Style Book"
Published April 23, 1996
Published by NEW's PUBLISHING Co., Inc.
2-4-7 Mishuku, Setagaya, Tokyo, 154, Japan.
Printed by Toppan Printing Co., Ltd.

Try this number: 03-5430-4441

Best I can do.