in the past if i didn't have enough funds in my credit card, i would choose the "pay by check" then when i get enough funds, i change the payment option to credit card.

now i don't think i can because when i checked out,they have this option "pay by check" but you have to enter your account number and stuff..

any idea if there's any alternative solutions?

yes, restraint.

They took away the check option a month or two ago. Now I think it's an instant transfer from your bank account, like PayPal uses.