Treasure boxes/baskets whatever you want to store them in are amazing, literally a selection of various items of items usually found in the home to encourage sensory and heuristic play. If you want to know more check out parenting project.
My box is and old Huggies baby starter kit box, and inside is various items including a book that crinkles, a wooden clothes peg, a make up brush, a loofah and exfoliating mitt and a curtain ring with ribbons tied to it. The items I grabbed were the curtain ring, as it is one of her favourites, a teether as she has a new tooth coming through, her little sheep and a shower scrunchie.
It was great to just slip the ribbon over the harness of the trolley when I strapped her in and know I wouldn't loose any toys, I also convinced another mum who was about to spent another £15 on yet another pram toy from Lamaze because her little one only a few months old was bored of theirs already, I told her to just tie some toys up with ribbon, it was cheaper and you can change it as the child changes, and she immediately put it back! Very naughty I know but she was having a tough time trying to choose something she thought the little one would like! I kept thinking about it on the way round and thought, after picking up a bag of limes and letting Alyssa play with them too, you could probably place smallish balls with bells in like cat toys, or other toys you cant really tie to ribbon, into a net washing bag and attatched that the the ribbon. My brain works in very strange ways. You could even just have Large beads atached to the ribbon as well, in fact there are lots of possibilities when you start thinking about it.
The ribbon also proved useful entertaining her whilst I was eating my tea later as well as she had finished and was fussing, I put it round my neck so she could play and again I didn't have to worry about her dropping things and picking them up constantly. The best part of the day though has to have been her giggling in the supermarket, whilst I threw the scrunchie over the side with exagerated "where did it go?' voices and faces only to magically make it appear again! The joy of children means you can act an idiot in public and nobody minds!!