What is included in the accessory kit for a 24-inch iMac? Thanks.

Everything but the iMac.

• Magic Keyboard with Touch ID
• Magic Mouse
• 143W power adapter
• Power cord (2 m)
• USB-C to Lightning Cable

Go to > iMac 24-inch - Technical Specifications - Apple and scroll down to " In the Box "

If you want upgrade and/or add extra accessories, you should do that when ordering on-line.

see > Buy iMac - Apple

If you purchase a pre boxed in-store model, then you maybe limited to the boxed accessories or the ones available at that location.