You could look into getting one of these (prepaid credit card found at a number of retailers)....

https://www.greendotonline.com/contents/login.aspx

They are not a line of credit, you only put money on there when you want to make a purchase and the monthly service charge is quite reasonable. It might be a good answer to needing a credit card. The other way you could do it is to have a paypal account verified with your bank account and do your purchases using the paypal system.