Helm Inc in MI is the official retailer of genuine Honda factory manuals, new and old, and is where I bought my NT service manual. Some of the older manuals are photocopies of the originals since they've been out of print for a long time. A great many manufacturers, including Ford & GM, use Helm for service literature to avoid having to store all that stuff themselves.
In the 80s, I did some moonlight work proofreading Haynes car and motorcycle manuals. It may have changed, but a common gripe at that time was having too many years and even models in one manual; for example, the manual for the Yamaha 250 DT-1 also covered the 125 AT-1, 175 CT-1 and 360 RT-1. This created a manual with a fair number of photos, drawings and sidebar notes not relevant to your model. I don't have any knowledge of Chilton but they could be in the same boat because it's difficult for any non-factory publisher to make money on a manual that only covers one year/one model.
