I bout a couple this last trip and they range around 3.95/ 4.95. They are nice adverage size coloring book and should not add a lot of weight unless you buy a lot of them. There are a lot of choices and all places do not have them all. I bought a pricess one and a MK games and puzzle one at a GF gift shop.
An idea- we bought these books (no more than $5- if that) and some color pencils when in the parks. We let DD and DS color while waiting on the curb for the parades and night shows- worked GREAT! Never heard a peep out of them the whole time!!! We will definitely do this again! We carry a regular size back pack and they fit great- they are regular size coloring books with lots of pages! And the kids both loved the pictures- great of the characters! This was the best idea we had the whole trip!