I agree with Skold, you could always get two or more lockers depending on how many people you have in your party and how much stuff you have.
I use this backpack, which doesn't have a ton of features, but I like because it is actually a large soft cooler. I throw freezer packs, canned drinks (non alcoholic), and lunches in the big pouch. Small pouch I use for
portable charger, cords, smaller snacks, and hygienic products. On hot days I also bring my
large but
portable fan (which is really high powered, a life saver on days where it feels like a hundred degrees), which I may still have room for in the backpack. The backpack is sometimes awkward to fit in a locker, so you might need to move stuff around/remove items from the bag.
On Hagrids on opening day, my gf and I had that backpack, several portable batteries/cords, tons of drinks and food, Nintendo Switch, umbrella, poncho, phones, and still had room to spare in our two small lockers.
For wands, there's only a couple of the largest wand
boxes which might not fit.
Here's one example. All the replica wands (Luna Lovegood's for example) should fit just fine, including the box itself. Here's a pic of Luna's wand box inside the small locker (card shown for size context):
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