This bicycle saddle bag is perfect

Roswheel saddle bag for road bike is easy to install and super simple to use. Inside, a neoprene compartment holds tools and protects tubes, and a hook holds your keys in place. Plastic piping protects the bag's edges and a reflective strap, compatible with a mini-light, makes you more visible to motorists.
This bicycle saddle bag is perfect for carrying your ride essentials. It's made of durable, water-resistant 600-denier polyester and attaches easily to your saddle with Velcro straps. For safety, it sports reflective trim and a taillight attachment loop.