Anything legitimate that I have ever seen requires a direct bank transfer. Why would anyone sell a bitcoin, which is irreversible once transferred, to someone who could make a chargeback if they paid with a credit card?
This is probably your best option if you want to buy purely with a card. However small quantities can usually be bought each time. You can always use LocalBitcoins to buy Bitcoin form other people with your paypal account, which you can tie your credit card to.