Roy Roger’s sidekick Pat Brady had a couple color books made under his name that feature a variety of nellybelle images. You can read more about nellybelle at the CJ-3B page.
1) This coloring book is for sale in a few different places. The cheapest price I found was on Etsy for $8.00 (plus shipping) and includes a few pages colored.
2) The cover of this coloring book was on a Pat Brady Biography page. I haven’t found it for sale anywhere yet.