A paper towel holder with page protectors attached by binder rings. How about an easy access dictionary for a writing center? What about a place to display student work? Oooo or a place to display artwork!
To expand upon this, the kids create a matching book with a picture of their structure (and their written description complete with labels,etc). You could also use a story telling app--creating a digital book to document and write about their work.
Fishpond New Zealand, Learning Stories: Constructing Learner Identities in Early Education by Wendy Lee Margaret Carr. Buy Books online: Learning Stories: Constructing Learner Identities in Early Education, ISBN Wendy Lee Margaret Carr