You can top-up your Suica with cash using the following methods.

[Convenience stores offering Suica top-up]
Inform the store clerk that you would like to charge (top-up) your Suica.

[Seven Bank ATMs (excluding some locations)]

[Lawson Bank ATMs (excluding some locations)]

[Charge (top-up) only machines supporting Welcome Suica Mobile]
Some stations have tray-style charge (top-up) machines that support Welcome Suica Mobile. 

Note: Charge (top-up) machines installed by some private railways, bus companies, or stores may not be compatible with Welcome Suica Mobile.