Small plastic container with notebook, pencil, sharpener and plastic dinosaurs. Large enough for a trackable or two.
Update - after the muggle of the original, the cache is now up in the air - hopefully this one is a bit more muggle-resistant.
Please ensure that you place the lid back securely and tightly to avoid rain damage.
Also - be aware of farm-worker muggles - they tend to pass the area during lunchtime and after 5pm.