Hi Teresa,
I believe you're asking about "Magic Bandits," the small embellishments you can add to your MagicBand to give it a bit of flair and personalization.
There is a small selection of Magic Bandits available for sale on
DisneyStore.com, but there are dozens of more options available at Walt Disney World. They are sold in many of the larger stores in the parks and resorts. You'll find the largest selection at the Emporium on Main Street in the Magic Kingdom and at Mouse Gear at Epcot, but there are loads of other buying opportunities as well. If you don't see them, just ask any cast member in the store.
As for PhotoPass, Disney goes through phases where they mail PhotoPass cards in advance and other phases where they don't. I believe that they are not currently mailing PhotoPass cards in advance, but there's some possibility this could change. Either way, it doesn't really matter much. You can get free PhotoPass cards from any PhotoPass photographer in the parks. And now you can link your PhotoPass pictures via your MagicBand. The photographer takes your photo then scans your wrist. The pictures are then automatically linked to your account. It couldn't be easier.
Have a great trip!