Photo from Rose & Grey
I'm with Myfanwy of Baby Gadget on this one. Why not make these totally cute Rustic Wooden Storage Boxes on Wheels from Rose & Grey? They'd look adorable as toy catch-all storage in a baby nursery and hey, creative reuse and no plastic!
Watch flea markets and antique stores for cool vintage wooden boxes and crates. Antique Mystique has some not-crazy-expensive ones too. And any hardware store sells wheels.