Purchased at a kid's store on Mississippi. It's this.
Reminds me of Jessica's project. They also make bigger ones. With triangles. Not sure I'll be able to resist!
P.S. Thanks for the heartwarming response to the call for quilt blocks! A few dozen are promised, and some are already in the mail to me from near and far. This is going to be a great project thanks to you. To borrow a phrase from Rachel, quilters rock!