The Green Windows ("midori-no-madoguchi") of JR stations sell ICOCA cards. The price of the card is 500 yen (about $5 USD), but at first you must pay 2,000 yen (about $20 USD), and you immediately get 1,500 yen (about $15 USD) of cash on the card. The limit you can have on the card is 20,000 yen (about $200 USD).