You are looking for a 2 x 4 inch camoflaged Lock&Lock container. Pretty simple find, nothing too complicated to it. Beware of muggles!
There is room for plenty of small trinkets, please be mindful about trading (Trade equal or up). Room for Trackables too.
Please rehide adequately, It shouldn't take more than a few seconds to do so
Brookline is a beatiful neighborhood with many fun public parks and places to have picnics, including across the street in Lawton Playground, where I looked unsuccessfully for a hiding spot. It was also the childhood home of JFK, whose house is closeby. Neighboring Allson also has fun parks and activities to do there.
Congrats to jorwant for the FTF!