well, actually, i’m getting one because a friend’s son is installing them as part of his Eagle Scout project. he was going to look into building them, and some people (including me) suggested newspaper boxes, so he approached local newspapers asking if they had any to donate to his project. all our local boxes were pulled off the streets years ago, so any that were still around were sitting in the newspaper’s storage yard, getting all rusty. he’s going to sand and prime them, and then the people who are getting them can either have him decorate them, or we can do it ourselves.
TLDR: call your local newspaper and ask! they might have some they want to get rid of.