I assume these are sold at the parks, but was wondering if these would be better to get before, not sure where they would be sold, but maybe there is more selection on these out there vs maybe only one type at the park? Do people make their own? If I were to wait and purchase these at the park, do they come with pen or marker, or do I need to get my own. I wonder how common these are, I have never had one going to WDW growing up so dont know how thick they should be.