My phone goes in my jersey's pocket. CO2 goes (one) in a lil' pouch along with a tire lever(one), and a tube (one). If any of them fails me, I am fooked only because I will have to hear it from my wife. Some time, I take my bottle and all that stuff goes inside except the cell phone.
https://www.google.com/aclk?sa=l&ai=DChcSEwje3u-JqdnbAhURxmQKHeLmBo0YABATGgJwag&sig=AOD64_1AeDWc-q0-3oWG4hKwOVpLzHJgeQ&ctype=5&q=&ved=0ahUKEwiS0OqJqdnbAhVVOH0KHUm8Ap4Q9aACCEM&adurl=
The big bag drives me nuts behind the seat. Over the years, I wrap all that in a ziploc bag and crank it down with duct tape and stuff it under the seat and strap it down with a Velcro to the seat rails. Its very small and tucks under there well.