Add real cash to members account

Hello All

I am new in here and not very techie,

I am running an Woocommerce store using the theme Mystile
I am looking for a plugin for members to add real cash to fund their account, if there is such a plugin,
The idea is for my members to fund their account throughout the year
and spend it in my store around Christmas time or purchasing a product for that special occasion, sort of like a savings system for them.

Any advice on this would be deeply appreciated.

Regards
Tony
http://kidsbatterypoweredcars.com/

http://wordpress.org/plugins/woocommerce/